could be commercially extracted and freed from its impurities. The results obtained will be found in Bulletin No. 60.

For Survey publications on chemical subjects, see the Survey's list of publications. A very large part of the work done for the geologists, however, is scattered through the various publications of the Survey; and in addition to the official publications the chemists have been frequent contributors to scientific journals, to the Smithsonian Miscellaneous Collections, and to the proceedings of chemical and other societies, both in this country and in Europe.

Section of Physics.

Physical research by the United States Geological Survey began in 1880, under direction of the geologist in charge of the division of California, when it appeared desirable to investigate the extraordinary thermal conditions of the Comstock Lode and to ascertain whether terrestrial electricity and magnetism were disturbed by the presence of ore bodies. The results are contained in Monograph III, on the Comstock Lode, and in the Annual Report for the year 1882.

At the close of this investigation, which was of course made in the field with portable and more or less extemporized apparatus, plans were prepared, under the direction of the late Mr. Clarence King, then Director of the Survey, for the equipment of a laboratory and the systematic study of certain geophysical problems under more favorable conditions. Most of the apparatus for this laboratory was constructed in Europe, the expense being borne personally by the Director, Mr. King. By November, 1882, the apparatus was received, and a private house in New Haven, Conn., was rented for use as a laboratory.

A brief classification of the researches proposed at that time is contained in the Second Annual Report of the Survey, and is of very considerable interest. If such a classification of the most important work to be done in geophysics were required to-day, after twenty years of marvelously active and productive work in most other branches of science, the classification then made would serve without the change of a word, so little attention has been given to geophysical problems as compared with those of other sciences.

The outline was this:

(a) Phenomena of fusion. These would comprehend temperature of fusion, specific volume at this temperature of the solid and of the liquid materials, respectively, heat expansion, compressibility, latent heat of fusion, specific heats-all considered with especial reference to their variation with pressure.

(b) Phenomena of elasticity and viscosity, considered, as before, with especial reference to their dependence on temperature and pressure.

(c) Phenomena of heat conductivity under analogous circumstances.

The establishment at New Haven was planned on a large scale and was intended to be permanent, but relatively little more than the

trying out of the plant and the determination of the instrumental constants was accomplished there.

In July, 1883, when a chief chemist of the Geological Survey was appointed, physics was incorporated with chemistry, and a concentration of all the laboratories of the Survey in Washington was determined upon. A year later the laboratory was established in cramped quarters in the National Museum, where temperature work on so large a scale as the New Haven plans contemplated appeared impracticable and had to be abandoned. Independent outside researches upon the effect of extreme pressure upon solids and upon high temperatures were, however, carried on under the general supervision of officers of the Survey.

From 1883 until 1892 research work at the Smithsonian Institution was continued without serious interruption.

The first independent official publication from the physical laboratory appeared in Bulletin No. 14 (1885), on "The Electrical and Magnetic Properties of the Iron Carburets," though the annual reports of the Survey and frequent contributions to foreign scientific journals gave ample evidence of the activity of the physical laboratory. The study of the iron carburets was a remarkably thorough one, continuing through a part of Bulletin No. 27 and all of Bulletin No. 35.

Perhaps the most important contribution to knowledge of high temperatures is contained in Bulletin No. 54, "On the Thermo-electric Measurement of High Temperatures." In this publication the fundamental measurement of temperatures upon the gas scale, up to and somewhat beyond the melting point of gold, was rescued from the confusion into which it had been thrown by the gas-thermometer measurements of Deville and Troost, in which iodine vapor was used above its (then unknown) dissociation temperature. The thermoelectric pyrometer became a practical and accurate laboratory instrument, and a new and unique method of measuring temperatures by the varying viscosity of gases was developed. This investigation has become so widely known and received such general recognition that its author was asked to write the report on high-temperature measurement for the great Congress of Physicists at Paris in 1900.

The entire work of those years occupies 15 bulletins and parts of a monograph and an annual report.

In 1892 the annual appropriation for chemistry and physics was reduced from $17,000 to $5,000, and physical research had to be entirely abandoned. So much of the apparatus as had been privately purchased was taken away, the laboratory was dismantled, and no further physical research was attempted until several years later.

In 1900 provision was again made to begin some work in physics, and a room was partitioned off for a laboratory on the fifth floor of the office building which the Survey now occupies. The physical and

chemical laboratories were then united under the official designation "division of chemical and physical researches." So little of the earlier equipment remained that all of the first year was spent in building and calibrating special apparatus and in general laboratory furnishing. Much more than usual difficulty was encountered in preparing for accurate physical measurements in the space assigned therefor, both on account of the location of the laboratory and on account of lack of the services of a skilled mechanic.

In the two years during which the laboratory has been in operation three researches have been undertaken. The most important one is a thorough and systematic thermal investigation of the relations of the feldspars, their melting temperatures, conditions of crystallization, etc. This experimental work is now approaching completion, but no results have yet been published. There have also been made measurements of the elastic constants of an interesting artificial pseudo-solid formed by beating the white of egg into a-stiff foam with a small quantity of sugar in solution, and of the linear force exerted by growing crystals.

For Survey publications relating to physics, see the Survey's list of publications. The physicists of the Survey have also made numerous contributions to other scientific periodicals and series.

TOPOGRAPHIC BRANCH.

The topographic branch is organized in two divisions-topography, and geography and forestry.

DIVISION OF TOPOGRAPHY.

Eastern and Western Sections.

The division of topography is divided for administrative purposes into two sections, the eastern and the western, but the work of the two sections is identical in character. The chiefs of these sections are the administrative heads, the one of all topographic surveys executed east of the one-hundredth meredian, and the other of all those executed west of that meridan. With the Director they form a committee having jurisdiction over all work of the division of topography. This includes a section of triangulation and computing, a section of inspection of topographic surveying and mapping, and thirteen subsections of topographic field work-three in the western section and ten in the

eastern.

The employees are procured through civil-service examinations held from time to time for the recruiting of the force. All appointments are to the minor position of topographic aid, and appointees are advanced by promotion through the grades of assistant topographer, topographer, and geographer, the latter title going with the larger administrative responsibilities.

Surveys may be divided into three classes:

1. Those made for general purposes, or information surveys, which may be exploratory, geodetic, geographic, topographic, geologic, etc. 2. Those made for jurisdictional purposes, or cadastral surveys, which define political boundaries and those of private property and determine the inclosed areas.

3. Those made for construction purposes, or engineering surveys, on which are based estimates of the cost of public and private works, such as canals, railways, water supplies, etc., and their construction and improvement.

The topographic survey, one of those in the first class, is made for military, industrial, and scientific purposes. The topographic map, made directly from nature by measurements and sketches on the ground, is the mother map from which all others are derived. It shows with accuracy all the drainage, relief, and cultural features which it is practicable to represent on the scale chosen.

The act of March 3, 1879, which created the United States Geological Survey, appropriated $106,000 for a geologic survey and classification of the lands of the public domain. The presentation of the results of a geologic survey necessitates a good topographic map. There was in existence no such map of the greater part of the public domain; therefore, of the sum appropriated, $19,624 was allotted for topographic surveys during the first year. In 1882, after the change of directors from Clarence King to J. W. Powell, and the extension of the work to "the preparation of a geologic map of the United States," the topographic branch was reorganized by the appointment of a chief geographer, and the work was divided into the northeast, southeast, central, and western sections of topography. The allotment for topographic surveys for the fiscal year 1882-83 amounted to $70,700, and necessitated a corresponding increase in the field force.

A similar organization of the topographic branch was maintained, with slight changes, until the beginning of the fiscal year 1888-89. An act making appropriations for the fiscal year ending June 30, 1889, provided the sum of $199,000 for "topographic surveys in various portions of the United States." Thus, while during the first decade of the existence of the Survey topographic surveys were executed as a necessary adjunct to geologic work and the classification of lands, at the beginning of the second decade the value of the topographic maps for other purposes had become so apparent that Congress provided specially for their preparation and publication.

During the first few years the present organization continued to use, in its map work, the same scale that had been employed by the earlier independent surveys-about 4 miles to the inch, or 1:250000, with relief shown by 200-foot contours; but when the cooperative surveys of the States were begun (see p. 60) it was seen to be desirable to increase the scale and contour interval, not only for the work in

those States, but for that in other States in which cooperation was not being carried on. This change was gradually extended to other regions, so that at the close of the first decade of the existence of the organization the scale and methods of work had been elaborated until they had reached practically their present status.

The earlier topographic mapping of the Survey was subjected to some criticism on account of lack of refinement in detail. It was a question of judgment whether the appropriation should be expended in accurately mapping a limited area or in making reconnaissance surveys over a more extended area. The less accurate maps were less expensive, and served a useful purpose in establishing the value of topographic surveys. The results have proved the wisdom of a policy whereby the people were gradually educated to the use of refined and detailed maps, while Congress learned to appreciate the cost and the comparative slowness with which accurate surveys would be prosecuted over so vast a territory as that of the United States. Had fewer square miles been mapped annually in the early years, but with the accuracy attained at present, it is doubtful if Congress would have continued to maintain the organization. As it was, valuable results were rapidly put forth, and in time it has been possible to supersede the older reconnaissance maps with more detailed maps, which serve as a basis for satisfactory delineation of the underlying mineral resources. As the topographic work steadily advanced, not only in scope, but in accuracy, it was found desirable to obtain from Congress authority to run careful spirit-level lines and to establish bench marks for permanent record of elevations upon the ground, and also to carry on control by triangulation or traverse with greater accuracy and to mark the positions more permanently than had been possible without statutory authority. Accordingly, on June 11, 1896, an act was approved which provided that "elevations above a base level located in each area under survey shall be determined and marked on the ground by iron or stone posts or bench marks," etc. Thereafter it was possible to provide for the running of careful spirit levels over all the areas under survey and to extend the amount of spirit leveling, thereby securing more accurate location of contours. Since that act was passed the topographic mapping has reached as high a degree of detail and quality as seems desirable for the scales adopted.

The features exhibited on the topographic maps of the United States Geological Survey are:

1. Hydrography, or water features, as ponds, streams, lakes, swamps, etc., which are printed in blue.

2. Hypsography, or relief of surface, as hills, valleys, and plains, which are printed in brown.

3. Culture, or features constructed by man, as cities, roads, villages, and the names and boundaries, which are printed in black.