Search Documents

By Frank Rieber

THE discovery that strongly magnetic bodies localized near the surface of the earth could be detected by the distortion which they produced in the resultant magnetic field marked the beginning of magnetic surveying methods. From an original ability to detect bodies of magnetic iron ore and the like when located very close to the, surface, these methods have been extended until today they promise to give much information with regard to the structure of such slightly magnetic material as sedimentary rock containing only a very small proportion of iron.1 The recent extensions have been made possible through the development of more delicate instruments, and of methods for their use. From the original compass and dip needle, the design of apparatus has progressed until equipment Is typified by magnetic balances capable of measuring the components of the earth's field to an extremely high degree of accuracy. It seems unlikely that the limit of such instrumental development has been reached. Just as the change from compass and dip needle has enabled the location of relatively minor changes in magnetic materials, so additional developments in the direction of increased sensitivity, as well as in greater dependability and constancy of operation, should reveal positively many slight changes which either escape notice in the present surveys or are so small that they cannot with certainty be separated from uncontrollable errors due to inconstant operation of the equipment. The ability to read smaller and smaller variations does not mean, of course, that deductions as to the causes of these variations will be made as accurately and definitely as -is possible with the more pronounced anomalies.

Jan 1, 1928

Jan 1, 1969

By O. G. Lellep

IN every country economic circumstances prescribe the method used to produce a commodity at lowest cost. In Pennsylvania a man's wages for working 4 hr buys a ton of coal wholesale; in Germany a laborer must work 40 hr, or ten times as long. In western Europe, therefore, conservation of fuel is of primary importance, and recent practices of burning lime and cement differ from those employed in the United States. This paper presents data collected during a trip through western Europe in 1953. Considered uneconomical, shaft kilns for burning cement disappeared in the United States two generations ago. But because required capital investment is low and operation greatly improved, shaft kilns are still used to some extent in Europe, where fuel costs are high, and are even included in designs for plants under construction. During the last 50 years shaft kilns have been maintained at the same physical size, while their output has been increased at least four times.

Jan 7, 1954

By C. E. Shoenfelt

Wildcat drilling in the Rocky Mountain region did not suffer as large a decline in 1942 as was anticipated. The drilling program laid out by the Government at the beginning of the year stressed wild-catting operations and called for reduction of drilling in proved fields. The increased wildcatting campaign did not yield a great many new discoveries, nor important extensions to old fields. Several interesting wildcat wells were drilled in Colorado in 1942 but no new fields were discovered. The Wilson Creek field was extended and about 400 acres added to its reserves. In Montana two new oil fields and two small gas fields were discovered. The developments in the marketing situation had improved, however, making the prospects especially bright for 1943, as will be shown presently in the section on Montana in this report. In New Mexico eight wells were completed, which constituted discoveries ol either oil or gas but none of these was of major proportions. In Wyoming one new oil field and one new gas field were discovered, and one old oil field and one old gas field were extended. Most important was the disco-very of prolific oil producers in deeper sands in three old oil fields, of which one at least, Elk Basin, probably is of major proportions. Government Action On Dec. 26, 1942, President Roosevelt signed the O'Mahoney bill, calling for a flat 12.5 per cent royalty on lands in the public domain. It is expected that the enactment of this bill will encourage wildcatting in the public land states. Opportunity for a full discussion of the problems of reserves and production was afforded at the hearings conducted on the O'Mahoney bill by the minerals subcommittee of the Senate Committee on Public Lands and the statements submitted at these hearings last fall placed the situation, its causes and the logical remedy, clearly on record. It was established at the hearings that for several years the volume of oil discovered per wildcat well drilled has steadily declined; new fields discovered have not been of major proportions; drilling costs have advanced rapidly; a sharp decline in exploratory drilling took place in 1942, while the proportion of dry holes increased; the inescapable conclusion is that to find new reserves the search for oil must be intensified and much more wildcat drilling ' must be done. To ensure an adequate drilling campaign, the Petroleum Industry War Council, the Interstate Compact Commission and other representative oil organizations have voiced by resolution their opinion that an upward revision of crude prices is necessary to provide an incentive to the prospector to undertake the hazards of wildcat drilling, since statistics prove that only ope in five or six wells drilled results in actual production. Former Price Administrator Henderson rejected the recommendations for price increases and declared himself unalterably opposed to a general price advance, On the ground that such advances would contribute to inflation. Now that Mr. Hender-

Jan 1, 1943

By C. E. Shoenfelt

Wildcat drilling in the Rocky Mountain region did not suffer as large a decline in 1942 as was anticipated. The drilling program laid out by the Government at the beginning of the year stressed wild-catting operations and called for reduction of drilling in proved fields. The increased wildcatting campaign did not yield a great many new discoveries, nor important extensions to old fields. Several interesting wildcat wells were drilled in Colorado in 1942 but no new fields were discovered. The Wilson Creek field was extended and about 400 acres added to its reserves. In Montana two new oil fields and two small gas fields were discovered. The developments in the marketing situation had improved, however, making the prospects especially bright for 1943, as will be shown presently in the section on Montana in this report. In New Mexico eight wells were completed, which constituted discoveries ol either oil or gas but none of these was of major proportions. In Wyoming one new oil field and one new gas field were discovered, and one old oil field and one old gas field were extended. Most important was the disco-very of prolific oil producers in deeper sands in three old oil fields, of which one at least, Elk Basin, probably is of major proportions. Government Action On Dec. 26, 1942, President Roosevelt signed the O'Mahoney bill, calling for a flat 12.5 per cent royalty on lands in the public domain. It is expected that the enactment of this bill will encourage wildcatting in the public land states. Opportunity for a full discussion of the problems of reserves and production was afforded at the hearings conducted on the O'Mahoney bill by the minerals subcommittee of the Senate Committee on Public Lands and the statements submitted at these hearings last fall placed the situation, its causes and the logical remedy, clearly on record. It was established at the hearings that for several years the volume of oil discovered per wildcat well drilled has steadily declined; new fields discovered have not been of major proportions; drilling costs have advanced rapidly; a sharp decline in exploratory drilling took place in 1942, while the proportion of dry holes increased; the inescapable conclusion is that to find new reserves the search for oil must be intensified and much more wildcat drilling ' must be done. To ensure an adequate drilling campaign, the Petroleum Industry War Council, the Interstate Compact Commission and other representative oil organizations have voiced by resolution their opinion that an upward revision of crude prices is necessary to provide an incentive to the prospector to undertake the hazards of wildcat drilling, since statistics prove that only ope in five or six wells drilled results in actual production. Former Price Administrator Henderson rejected the recommendations for price increases and declared himself unalterably opposed to a general price advance, On the ground that such advances would contribute to inflation. Now that Mr. Hender-

Jan 1, 1943

By C. R. Van Hise

PART I.-GENERAL PRINCIPLES. [ ]

Jan 1, 1902

By F. R. Koeberlin

ABOUT thirty miles south of the port of Coquimbo, Chile, nestling in one of the western outliers of the main Andes range, lies the little mining town of Andacollo, a place whose history and traditions make up one of the most romantic pages in the life story of this southern republic. The beginning of Andacollo is shrouded in the penumbra of the pre-Columbian era, but its first mining activity probably dates from about the years 1440 to 1460. It was in the middle of the fifteenth century that the Inca Tupac-Yupanqui, grandfather of Atahualpa, conquered this part of Chile. His domain extended even as far south as the present site of Santiago, and perhaps farther, but was maintained with increasing difficulty against the fiercely independent and indomitable tribes of Araucanian Indians of the South.

Jan 1, 1938

By B. Silliman

THE remarkable outflow of natural gas recently developed in Western Pennsylvania, and along the valley of the Ohio and its tributaries, has called attention to an important series of patents for improvements in glass-fnrnaces and the manufacture of glass, which the brothers Siemens have made since 1872. The basement-patent of this series, is No. 127,806 of the U. S. Patent office, and is of date June 11th, 1872. This has been followed by eleven other patents (including one re-issue), all for improvements in glass-furnaces, or methods of manufacture, of which the latest is of date July 11th, 1882. Nine of these patents were issued in 1880-82. The following is the list of these patents, in order of dates, viz.: 1872. June 11th. No. 127,806 (U. S. office), Improvement in glass-furnaces; 17 sheets drawings, 5 pages text. This is the basement-patent. 1877. April 17th. No. 139,800. Improvement in the manufacture of glass; 3 sheets drawings, 2 pages text. Boats and floating vessels swimming in the liquid glass of the tank-furnace. Re-issued in 1880. q. v. 1880. April 27th. No. 226,931. Furnace for annealing and tem pering glass. " July 13th. No. 220,846. Glass-melting-furnace. " August 3d. No. 230,668. Glass-melting-furnace; 4 sheets drawings, 2 pages text.

Jan 1, 1885

By Edward J. Felten

THE oxidation resistance of chromium and Fe-Cr alloys is increased by small additions of yttrium or other rare earth metals.1,2 In addition, the presence of the additives increases the resistance of these alloys to spalling of the external oxide above 1000°C. This ability to prevent spalling appears to be related to the formation of an internal oxide in alloys containing yttrium or the other rare earth metals. The internal oxide is found in the form of a filamentary growth concentrated in the grain boundaries of the unoxidized metal. In alloys containing yttrium this internal oxide was found to be either Y2O3 Or YCrO3.' In an earlier report,' the growth of the external oxide was found to be controlled by diffusion through the oxide layer. Thermal balance studies were used to establish the kinetics of external oxide formation. In this related study the rate of growth of the internal filamentary oxide has also been studied. The results obtained indicate that the growth of the internal oxide is also diffusion controlled. Internal oxidation appears to occur in at least two ways. Using copper alloys containing small amounts of silicon, Rhines 3 found that between 600" and 1000oC a subscale was formed which consisted of particles of silica dispersed in the metallic matrix. The conditions requisite to internal oxidation as suggested by Rhines are: 1) a solubility of oxygen in the alloy, 2) the ability of oxygen to diffuse at an appreciable rate into the alloy, 3) the possibility of the formation by the alloying element of an oxide more stable than the oxide of the host metal, and 4) a relatively low solubility of this oxide in the metal. These conditions are fulfilled for a number of other copper alloys.3-5 Furthermore, the relationship between the depth to which the internal oxide is formed and the oxidation time follows the simple parabolic law.6 The activation energy for copper containing small amounts of silicon, germanium, iron, or manganese as calculated from Rhines data6 is about 48 kcal per mole. In some cases the internal oxide is found segregated at the grain boundaries, especially near the the surface. Observations of this type of oxide formation have been reported by stead,7 Rhines,* and Lustman. Evans" cites these cases as examples of the simultaneous movement of anions and cations during oxidation. Furthermore, Evans states that the presence of a minor constituent with a high

Jan 1, 1962

By T. S. Mohibatsela, R. V. Ramani, C. V. Manula

The Mineral Engineering Department of The Pennsylvania State University has developed a suite of computer models for anthracite open pit mining (Fig. 1)1 Individual sub-systems have been developed to (a) interpolate geologic field data to obtain coal tonnages, waste volumes, and strip ratios; (b) simulate equipment performance on selected pit profiles to generate data required to choose coal and waste removal equipment; and (c) evaluate selected cost factors to determine either a rate of return for a specified selling price or vice-versa. This paper describes the application of two of these subsystems, namely, the Reserves Model (GEOL) and the Open Pit Materials Handling Simulator (OPMHS), and how these may be applied for the selection of equipment for a prime anthracite mining site.2

Jan 1, 1981

By C. A. Hartnagel

The production of petroleum in New York state in 1942 amounted to 5,410,000 bbl. This represents an increase over each of the four preceding years, and, with the exception of 1937, is the largest production since the peak of over six million barrels in 1882, shortly after the discovery of oil in Allegany County. The oil industry in New York is virtually stabilized and there has been little or no exploration for new sources of supply in recent years. The boundaries of the present fields were established more than 30 years ago and since then no additional reserves have been found. Deep drilling for natural gas during the past 10 years both within and without the oil fields has failed to find oil in quantity below the present producing sands of Devonian age. Oil Since 1882, the New York fields have produced approximately 140 million barrels of oil. Of this amount, 65 million was produced up to the year 1919 by ordinary pumping methods; that is, without flooding by water or the use of other secondary-recovery methods. In the year 1919, when a law was passed making the use of water-flooding methods legal, the oil production, of the state amounted to only 851,000 bbl. In the 23 years since 1919, there have been produced in the state 75 million barrels, or 10 million more than in the previous 37 years, which included the period of flush production. Price.—On March 26, the price of crude oil was raised from $2.75 to $3.00 per barrel, hut this increase had little or no effect on the number of wells drilled. In the Allegany field, which accounts for three fourths of the state's oil production, 1259 wells were completed in 1942, 7 less than in 1941. The smaller number of wells drilled was not only due to the shortage of labor but also was caused by the fact that in water-flooding territory a definite program for drilling wells is followed, and the flush period of an oil well is not usually reached in time to profit by any given price increase. Daily Production.—All of the oil wells in New York state, some 21,000 in number, are small producers. The average daily oil production is 7/10 bbl. per well. Under good flooding conditions, a maximum production of 5 to 8 bbl, a day is reached about one year after the flood begins to act on the well. In 5 years the daily production usually is less than one barrel. Although most of the oil in New York is produced by flooding, an estimated 2500 old wells produce without flooding. Some of these produce as little as 1/20 bbl. a day and are pumped only at intervals. The small producing Wells are mostly on lands leased to the larger oil companies and later will be included in a flooding program. At present, they are pumped only because the owners of the land insist on the royalty. Government Aid Needed.—Because of its good lubricating qualities, New York oil is one of those for which there is an insistent and growing demand, but even at its present price of $3.00 per barrel, many of the operators are producing at a loss.

Jan 1, 1943

By C. A. Hartnagel

The production of petroleum in New York state in 1942 amounted to 5,410,000 bbl. This represents an increase over each of the four preceding years, and, with the exception of 1937, is the largest production since the peak of over six million barrels in 1882, shortly after the discovery of oil in Allegany County. The oil industry in New York is virtually stabilized and there has been little or no exploration for new sources of supply in recent years. The boundaries of the present fields were established more than 30 years ago and since then no additional reserves have been found. Deep drilling for natural gas during the past 10 years both within and without the oil fields has failed to find oil in quantity below the present producing sands of Devonian age. Oil Since 1882, the New York fields have produced approximately 140 million barrels of oil. Of this amount, 65 million was produced up to the year 1919 by ordinary pumping methods; that is, without flooding by water or the use of other secondary-recovery methods. In the year 1919, when a law was passed making the use of water-flooding methods legal, the oil production, of the state amounted to only 851,000 bbl. In the 23 years since 1919, there have been produced in the state 75 million barrels, or 10 million more than in the previous 37 years, which included the period of flush production. Price.—On March 26, the price of crude oil was raised from $2.75 to $3.00 per barrel, hut this increase had little or no effect on the number of wells drilled. In the Allegany field, which accounts for three fourths of the state's oil production, 1259 wells were completed in 1942, 7 less than in 1941. The smaller number of wells drilled was not only due to the shortage of labor but also was caused by the fact that in water-flooding territory a definite program for drilling wells is followed, and the flush period of an oil well is not usually reached in time to profit by any given price increase. Daily Production.—All of the oil wells in New York state, some 21,000 in number, are small producers. The average daily oil production is 7/10 bbl. per well. Under good flooding conditions, a maximum production of 5 to 8 bbl, a day is reached about one year after the flood begins to act on the well. In 5 years the daily production usually is less than one barrel. Although most of the oil in New York is produced by flooding, an estimated 2500 old wells produce without flooding. Some of these produce as little as 1/20 bbl. a day and are pumped only at intervals. The small producing Wells are mostly on lands leased to the larger oil companies and later will be included in a flooding program. At present, they are pumped only because the owners of the land insist on the royalty. Government Aid Needed.—Because of its good lubricating qualities, New York oil is one of those for which there is an insistent and growing demand, but even at its present price of $3.00 per barrel, many of the operators are producing at a loss.

Jan 1, 1943

Jan 1, 1959

By Albert Sauveur

THE senior author of this paper has expressed the belief that when gamma iron transforms into alpha iron on reaching the A3 point, each gamma grain does not change bodily into one or more alpha grains but that the alpha phase forms first at the boundaries and along the crystallographic planes of the austenite grains.1 To quote: On cooling through the point A, at about 900° C., iron passes from the gamma condition to a. new allotropic form generally designated as alpha. This transforma¬tion, however, is not instantaneous. There are good reasons for believing that it begins at the grain boundaries and along the octahedral planes of the crystals and that it progresses until each grain of gamma iron is changed into a grain of alpha iron, the resulting structure being similar to that of gamma iron. Were it possible to retain at room temperature pure iron but partially transformed, it seems probable that a Widmanstättian structure, or rather, as later explained, a martensitic structure would be observed (Fig. 1), consisting of alpha iron at the boundaries and at the octahedral planes, and of a groundmass of gamma iron. In order to confirm, if possible, the accuracy of that view, a number of experiments were conducted. Polished samples of electrolytic iron were heated in a vacuum, maintained in the gamma range for several hours and quenched in different media. It was hoped by such means to produce and retain on the polished surfaces a pattern which would reveal the mechanism of the allotropic transformation. The samples were placed in evacuated quartz tubes, heated to 1000° C. and held 2 hr. at that temperature. The tubes were then immersed in the quenching bath. Iced brine and liquid air were used first. The polyhedral austenitic structure existing at the time of immersion was very clearly revealed (Fig. 2). This is generally ascribed to iron volatilizing at the grain boundaries.

Jan 1, 1929

By Alfred Boyles

"Heredity"1 in cast iron has been a subject of much discussion. Numerous experimenters have found that the properties of gray iron may vary greatly without corresponding variations in composition or thermal treatment. The main structural difference in such cases is in the size and distribution of the graphite flakes and the explanations given usually attribute this difference to some chemical element not shown by ordinary analysis or to some physical factor, such as inclusions in the melt. It cannot be said that any of these theories is completely satisfactory. Much remains to be learned about cast iron and for this reason a study of the material was undertaken as a part of the program of fundamental research at Battelle Memorial Institute. A review of the literature indicated that very little systematic work had been done on the mechanism of freezing in cast iron. The experiments described below are largely concerned with that problem. Normal and "Dendritic" Cast Iron As examples of variation in type of structure, photomicrographs of two test bars of cast iron are shown (Figs. 1 and 2) and the composition and properties are given in Table 1. Both are common, unalloyed gray iron. Test bar No. 13 has normal graphite flakes while No. 49 has very fine, lacy graphite arranged in a dendritic pattern, the matrix in both being pearlite. These two types of cast iron are well known to foundry-men and need no detailed description.

Jan 1, 1937

By William T. Folwell

The Lucky Friday mine east of Mullan, Idaho, is an outstanding example of a property in the Coeur d’Alene district where a small and insignificant- appearing silver-lead-zinc vein at the surface has changed at depth into a large vein of great importance. The Lucky Friday vein has little if any surface expression and above the 1200 level the ore shoots are small and discontinuous. Between the 1200 level and 2450 level, the lowest developed level, the main ore shoot has shown remarkable improvement on each succeeding lower level, and today the mine is one of the major lead-silver producers in the Coeur d'Alene district. History: The Lucky Friday property is on the north side of the South Fork of the Coeur d'Alene River in sections 25, 26 and 35, T. 48 N., R. 5 E., Hunter mining district, Shoshone County, Idaho. This is about one mile east of the town of Mullan, which serves the eastern portion of the Coeur d'Alene district. The southern part of the property is crossed by a branch line of the Northern Pacific Ry. and by U. S. Highway 10. This highway is the principal road crossing the panhandle of Idaho and connects the district with Spokane, Wash., on the west and Missoula, Mont., on the east. The main portal and surface plant of the Lucky Friday mine is at an elevation of 3365 ft, only a short distance above the valley floor and a few hundred feet from U. S. Highway 10, so the mine is readily accessible for year-round operation.

Jan 12, 1958

By G. Howell Clevenger, Bhupendranath Ray

Formerly great divergence of opinion existed in regard to the influence of copper in steel, as affecting its various physical properties. More recently the investigations of Stead,l Breuil,2 Wigham,3 Burgess and Aston: Ball and Wingham,5 Miiller; Dillner,7 and others have shown fairly good agreement in the major points. Copper steel has been shown by these investigators to possess special properties which make it valuable for certain uses. The general range of composition of the useful alloys of copper and iron, and of copper, iron, and carbon, has been quite definitely established, for the former by Burgess and Aston,8 and for the latter by Breuil9 and Stead.10 Stead11 has removed one difficulty in reconciling certain of the earlier data by calling particular attention to the influence 'of carbon in copper steels. Another point which caused confusion in the earlier investigations, particularly in regard to " red-shortness," was the presence of sulphur. Failure to note the presence of sulphur often led to attributing " red-shortness" to the presence of small amounts of copper. Turner12 has called attention to the fact that where copper exists in an iron ore it often occurs as the sulphide, so that the presence of copper in steel made from such ores might also, necessarily, mean the presence of sulphur. It is evident that the effect in this case might be quite different than where pure copper was added.

Jan 1, 1914

By Otto Wartenweiler

AFTER the phenomenal development of the new mine, the United Eastern Mining Co., with Mr. Frank A. Keith as President, decided to install a reduction plant. The character of the ore, closely resembling the product of other mines in the district, did not offer any particular metallurgical problems, since these neighboring mines had been operating milling plants very successfully for several years. Thus, with the general metallurgical treatment fairly well-defined, the matter of next importance was to design and construct a plant as economically as possible, that would give the best results obtainable. The ore consists of a mixture of calcite and quartz in about equal quantities with some decomposed andesite, while the average value of mill heads were calculated to be $20 plus in gold, no silver being present. The tonnage to be treated at ,the start was fixed at 200 tons, but, in view of the favorable condition of the mine, it was considered advisable to arrange facilities, for increasing the capacity to 400 tons. . While it is best in some cases to adopt a distinct independent unit system where future enlargement is contemplated, in this instance the plans worked out differently. Summarized, the treatment adopted consists of coarse crushing, coarse grinding, fine grinding and cyanidation. For coarse crushing the selection of the No. 6 size gyratory crusher was governed not so much by its capacity as by the size of the feed openings to properly receive the run-of-mine material, which was too coarse for a No. 5 crusher. To accomplish the coarse grinding to. best advantage, a careful comparison was made between the modern steel ball mill-the last word in crushing and grinding-and one of its older, and, at that time better-established, competitors, the rolls.' The following conclusion was reached: While it is possible that for the sized plant under consideration the cost of operating rolls might be a little cheaper, it is preferable to use ball mills because a simpler arrangement is possible, and1 because. the handling of, ball mills is preferred by the operator.

Jan 11, 1917

L. D. GODSHALL, Everett, Washington: This very interesting paper cannot fail to command the attention of every one who has ever had experience in the amalgamation of gold-ores. I wish to call attention to three very important facts brought out very prominently by the paper, namely: 1. The extent of accumulation of amalgam on copper plates in the form of scale, not removable in the ordinary manner; 2. The change in the relative quantity of the two metals in the amalgam as we. recede from the battery-discharge; 3. The difference in fineness of the bullion obtained from the above-mentioned scale as compared with the bullion from the daily clean-ups. From Mr. Bayliss's figures we find that during the life of the plate in question 14,942 tons of ore were crushed, yielding amalgam of the value of $5.03 per ton, or a total value of $75,158.26. The amalgam accumulating on the plate during this time as scale, we find to have had a value of $8340.54, or $0.558 per ton of ore treated, representing 11.09 per cent. of the total amount of amalgam saved in the ordinary clean-up; or, taking the amalgam saved by daily clean-up plus the amalgam-scale as representing the total saved on this plate, or 100 per cent., we find that the daily clean-up saved 90.01 per cent., while the scale represented 9.99 per cent. The above figures do not include some additional amalgam still adhering to the plate after scale had been removed. We are told that this was not an exceptional case at the Drum Lummon, but that other plates have even yielded a third more than the one in question. The interesting query now comes up, whether this experience at the Drum Lummon is exceptional or universal at all mills; and another question arises, as to how long such an accumulation might continue,

Jan 1, 1897

By John B. Hastings

THE reconnaissance of the Goldfield mining-district, described in this paper, was made in May and June, 1905, and, though this time was too short for a complete report, the work accomplished may serve as a basis for more thorough future research. Dr. Berkey has examined the rocks collected by myself, and I am using his classifications. As a result of further field-work, and Dr. Berkey's examination of the rocks, this paper is an elaboration and correction of my views expressed in the Gold-field Sun, May 12, 1905. The sketch-map, Fig. 1, illustrates the geology of the Goldfield mining-district. Goldfield is an eruptive complex, consisting of alaskite (binary granite), hornblende-andesite, hornblende-dacite, rhyolite, pyroxene-andesite, pyroxene-dacite (sometimes containing, a small quantity of olivine), quartz-felsite, olivine-pyroxene-ande¬site, and basalt. Considering this list to be arranged in the order of eruption, the age-sequence of the rocks conforms to Richthofen's law, formulated in 1868. From his observations in Europe and America, propylite, andesite, trachyte, rhyolite and basalt, occurring together, succeed one another. In a general way, the medium and more acidic rocks precede the most asic-a result supposed by some to have arisen from their relative position beneath the surface, and due to a rude stratification by gravity in the original cooling magma during the older history of the earth, or to the same differentiation occurring during a quiescent (molten ?) period preceding eruption, being aided by the ease with which acidic rocks, mixed with water vapors, become fusible. In effect, the more basic and less re-

Mar 1, 1906