October 8, 1908' 



A^.-7 TURE 



500 



Mr. Clarke's mineralogical researches and his connection 

 with the laboratory of the L'nited States Geological Survey 

 well qualify him for a task of this kind. 



The volume begins with a brief notice of the chemical 

 elements, as regards their distribution and relative abun- 

 dance in the known part of the globe, a subject to which 

 the author has himself made some interesting contribu- 

 tions. Then follows a valuable summary, from the chem- 

 ical point of view, of the nature of the atmosphere, the 

 waters and saline contents of rivers, lakes, seas, and 

 springs, and the gaseous constituents of igneous rocks, 

 volcanic emanations, and fumeroles. A large number of 

 analyses of air, waters, and gases are collated, and their 

 bearing on some of the questions of physical geology in- 

 dicated, with an occasional discursus upon such subjects 

 as the composition of the primitive atmosphere and flie 

 source of volcanic water and gases. 



This occupies one-third of the volume. About half as 

 much space is devoted to igneous rocks and their con- 

 stituents. In this department any trustworthy data, 

 beyond chemical analyses, are at present vei-y scanty. The 

 admirable work of Day and others at Washington, while 

 providing us with accurate thermal constants for a few of 

 the rock-forming minerals, has at the same time dis- 

 credited practically all previous results in the same line. 

 It appears, for instance, that the melting-point of anor- 

 thite, one of the most easily crystallised minerals, has been 

 underestimated to the extent of 400°. The account here 

 given of the several rock-forming minerals is accordingly 

 little more than what is to be found in any text-book, ex- 

 cepting that the information concerning artificial reproduc- 

 tion of the minerals is brought down to date. The space 

 might have been more profitably filled by a section written 

 on the lines of the " Synthase des Min^raux et des Roches " 

 of Fouqu^ and Michel-L^vy. The fifty pages dealing with 

 igneous rocks, under a peculiar scheme of classification, 

 might well have been omitted. No useful purpose is served 

 by selected analyses of rocks in a work of this kind, when 

 complete collections of analyses are easily accessible. 



The remaining chapters treat of the decomposition of 

 rocks, sedimentary and detrital rocks, metamorphic rocks, 

 metallic ores, the natural hydrocarbons, and coal. Under 

 the last two heads especially there is a large amount of 

 information which we have not seen elsewhere brought 

 together in so complete a form. 



The United States Geological Survey, taking a liberal 

 view of its province, has from time to time issued publica- 

 tions dealing with general geological subjects, and among 

 these the one now before us will take its place as a useful 

 work of reference. It will be the more valued because 

 the material is presented in a concise form, and the volume 

 is of such size as to be easily handled without the aid of a 

 lectern. A. H. 



THE INFLUENCE OF HUMIDITY ON 

 RESISTANCES. 



A/TESSRS. ROSA AND BABCOCK, at the Bureau of 

 Standards, found that manganin wire resistances 

 used in resistance boxes varied according to the time of 

 the year ; for instance, in summer they were 0-015 P^i" 

 cent, to 0-025 P^i" cent, higher in value than they were 

 in the same temperature in winter. These experimenters 

 e.xplain this periodic variation by the fact that with in- 

 creased relative air humidity the shellac, especially that 

 between the metal tube and the wire, swells ; the base 

 on which the wire is wound consequently increases in 

 diameter, and the forces thereby created cause the resist- 

 ance wire to expand elastically. With decreasing humidity 

 the shellac gives off moisture and shrinks, the pressure on 

 the wire is relaxed, and the resistance decreases. 



Tests just completed, and the results published (Zeit- 

 schn'ft fiir htstriimenien'kuiiie, .August), by the Reichs- 

 anstalt go to confirm this view, but the variations observed 

 then? are much slighter than those found at the Bureau 

 of Standards. The tubes on which the wire is wound 

 had hitherto been covered, first of all, with a sheet of 

 silk, this being well covered with shellac ; but in view 



of the humidity effect, tests were made with a number 

 of specially prepared lacquers, but, so far as obtaining 

 one which was impermeable to moisture was concerned, 

 the experiments were futile. The author has therefore 

 tried the effect of rendering the tubes to a certain degree 

 elastic in order to combat the effect of the expansion 

 mentioned, and has found that by providing them with 

 longitudinal slots, and also dispensing with the preliminary 

 covering of silk, a considerable advance has been made in 

 this connection. In one coil mentioned in the results the 

 six slots projected on both the upper and under sides to 

 the extent of 3 mm. beyond the windings, while in another 

 tube the slots on the upper side projected i cm. beyond 

 the wire, reaching to the same distance as the wire on 

 the under side. These coils were measured immediately 

 after construction, and attained a constant value in a much 

 shorter time than did the coils constructed hitherto. 



With a view to obtain the maximum accuracy, the 

 author also suggests that the resistance boxes should be 

 continually filled with parafifin oil of a density of about 

 0-86. Whether better results will really be obtained in 

 this manner is at present the subject of experiment. 



The test coils experimented on up to the present are, 

 without exception, the long, thin form usual in resistance 

 boxes. .\ few slots will not suffice for rendering more 

 elastic the short, wide tubes used for standard resistances. 

 It must remain for tests to ascertain what is the best 

 form for these coils, and a research is already in hand 

 with this obect. 



The paper gives a full description of the experiments, 

 and contains a number of curves showing the variations 

 of a number of coils at the Reichsanstalt. 



THE OPENING OF THE MEDICAL SESSION. 



T^HE medical year of the schools of medicine in London 

 and the provinces may be said to commence on or 

 about October i, and the opening of the session is in 

 many instances made the occasion for the distribution of 

 prizes, the delivery of addresses of welcome and advice, 

 and the re-union of old friends at the " old students' 

 dinners." 



At University College, after the distribution of medals 

 and prizes by the Dean, Dr. Batty Shaw, Sir Edward Fry 

 addressed the students and their friends. He first offered 

 his congratulations on the admirable buildings in which 

 the work of the school is now carried on, and then made 

 some remarks on the professional ideal. The advantage 

 of a profession over a trade is that it sets a higher ideal 

 before a man ; it requires of him to benefit the persons for 

 whom he acts without regard to any private interest of 

 his own. The legitimate gain which must accrue will be 

 a secondary object rather than a primary one. It is on 

 this ground that, quite justly, the world expects of pro- 

 fessional men a higher standard of intelligence and of 

 morals than it requires of the mere tradesman. Every 

 true student should be a student all his life through ; he 

 should be able to say with old Solon, " I grow old always 

 learning many things." Finally, Sir Edward touched on 

 the relation of the medical profession and the State, point- 

 ing out that it is obvious that the medical profession is 

 becoming more and more occupied with public business, 

 and that its aid is being more and more invoked by the 

 governing authorities. He referred to the investigations 

 that are being made by the direction of the Privy Council, 

 the various commissions that are being issued dealing with 

 tuberculosis and other aspects of disease, the scheme now- 

 being put into practice for the medical examination of 

 scholars in the primary schools, and the appointment of 

 medical officers of health throughout the country. The 

 medical profession is being drawn in an increasing degree 

 closer to the work and objects of the State. However 

 close that relationship may become in the future, it is 

 hoped that the medical profession will strive to maintain 

 its independence, and will never believe that it is to be 

 subservient to the State. 



.At King's College Dr. .Alexander MacAIister delivered 

 an address on fifty years of medical education. After 



NO. 2032, VOT,. 78] 



