April 16, 1903 



NA TURE 



573 



The present report enumerates the position of all these 

 stations, and tabulates the values of the declination, inclina- 

 tion and horizontal force as observed, and as reduced to the 

 common epoch January i, 1900. The data are also embodied 

 in a series of charts. In the reduction to a common 

 epoch the secular change was derived from numerous 

 absolute observations made at Linden, Montgomery 

 County ; whilst diurnal variations were deduced from 

 the records of the Naval Observatory, Washington. Un- 

 fortunately, owing to the disturbing action of electric trams 

 at Washington, no satisfactory data were obtainable for the 

 actual years occupied by the survey, and recourse was neces- 

 sarv to earlier records, mainly of the three years 1889 to 189 1, 

 particulars of which appear in the report. This, of course, 

 is open to objection, on the ground that the amplitudes of 

 the diurnal inequalities of the several elements vary from 

 year to year. However, as both the magnetograph records 

 and the field observations relate to years of relatively small 

 sun-spot frequency, the objection is less serious than might 

 appear at first sight. 



Calculations are given of the probable errors in single 

 observations with the instruments employed. The results 

 appear fairly satisfactory in the case of the declination and 

 inclination, but less so in the case of the horizontal force 

 (cf. Table 18, p. 84). Dr. Bauer considers the weak point 

 in the magnetometer — of the Geodetic Survey's old pattern — 

 to have been the employment of wood in the deflection bar, 

 and he states that the U.S. Sjirvey is now procuring a 

 superior type of instrument. One point that may be also 

 worth reconsidering in this connection is the employment of 

 35 and 49 cms. as the two distances for deflections in hori- 

 zontal force observations. Large distances have the ad- 

 vantage of reducing the uncertainties connected with the law 

 of force between two magnets of finite size ; but except in 

 regions where the horizontal force is very low, distances such 

 as 35 and 49 cms., with magnets of ordinary strength, imply 

 small deflection angles, and the writer is inclined to think 

 this may more than compensate for any theoretical advan- 

 tage, especially in field work. 



One of the interesting points discussed, and illustrated in 

 the charts, is the existence of a considerably disturbed region 

 near Gaithersburg, some twenty or thirty miles north-west of 

 Washington. The abnormalities here were apparently first 

 disclosed by special observations made with a view to the 

 selection of a site for a magnetic observatory near Washing- 

 ton. The fact emphasises the dangers to which random 

 choice of such a site may be exposed. At the end of the 

 report there is an outline of a scheme for the complete mathe- 

 matical investigation of the magnetic distribution in Mary- 

 land, but the working out of this and various other details 

 is postponed, pending, apparently, the elaborate survey of 

 the entire United States which the U.S. Coast and Geodetic 

 Survey has now in contemplation. C. C. 



SCIENTIFIC SERIAL. 



American Journal of Science, March. — Studies of Eocene 

 Mammalia in the Marsh collection, Peabody Museum, by 

 J. L. Wortman. Part ii. Primates. — On eerie chromate, 

 by P. E. Browning and C. P. Flora. An excess of chromic 

 acid precipitates a eerie chromate of the composition 

 Ce(CrO.,),,2H,0 from solutions of cerium salts. Although 

 the sulphates of lanthanum, didymium and yttrium were 

 present, these metals were not present in the precipitate. — 

 The effects of changes of temperature on permanent mag- 

 nets, by H. B. Loomis. After giving a historical resume' 

 of previous work on this subject, experiments are described 

 showing the changes in the magnetic moment of magnets 

 of different lengths, but of the same cross section, and on 

 the change in distribution due to change of temperature. — 

 On the chemical composition of axinite, by W. E. Ford. 

 Expressed as an orthosilicate, the formula is found to be 

 CajAl^SiOJ,, in which the calcium may be in part re- 

 placed by varying amounts of Mn, Fe, Mg, and hydrogen, 

 while a little Fe is isomorphous with the Al. — The electrical 

 conductivity and absorption of energy in the electrodeless 

 discharge, by Bergen Davis. — The geological structure of 

 New Mexican Bolson Plains, by C. R. Keyes. — Note on the 

 marine turtle Archelon. (1) On the structure of the cara- 



NO. I746, VOL. 67] 



pace ; (2) associated fossils, by G. R. Wieland. — The ionisa- 

 tion of water and of phosphorus nuclei, by C. Barus. — On a 

 method of demonstrating Newton's rings by transmitted 

 light, by H. N. Davis. If a number of wire rings of the 

 same size be mounted in parallel planes, and dipped together 

 in a soap solution, their planes being kept perpendicular to 

 its surface, a series of films results through which light 

 can be passed and caught on a sheet of paper, showing very 

 beautiful colour phenomena. — Note on the amphibole 

 Hudsonite previously called a pyroxene, by S. Weidman. 



SOCIETIES AND ACADEMIES. 

 London. 



Royal Society, March 26. — " An Attempt to Estimate the 

 Relative Amounts of Krypton and of Xenon in Atmospheric 

 Air." By Sir William Ramsay, K.C.B., F.R.S. 



In these experiments 191-1 kilograms of gaseous air were 

 passed into a Hampson's liquefier, and 11 3 kilograms of 

 air were liquefied. This liquid air was evaporated in a partial 

 vacuum, until only about 200 cubic centimetres remained. 

 1 he residue, consisting largely of oxygen, and also con- 

 taining argon, krypton and xenon, was deprived of oxygen 

 and nitrogen by means of red-hot copper and magnesium 

 lime, and the resulting mixture was fractionated, so as to 

 separate the argon, krypton, and xenon. Complete separ- 

 ation was not achieved, but knowing the densities and 

 volumes of the fractions of gas obtained, their relative 

 amounts could be calculated. This method does not pre- 

 clude loss of the rarer gases, but that loss, especially in the 

 case of xenon, must have been small ; the vapour-pressure 

 of krypton at the temperature of fractionation, —195°, being 

 only 2-8 mm., and that of xenon, 002 mm. 



The results are reproduced in the following tabular state- 

 ment : — 



Percentage krypton in gaseous air, o 000014 by weight. 



Percentage xenon in gaseous air, 00000026 by weight. 



Krvpton equal to 1 part by weight in about 7 millions of 

 air ; by volume, 1 part in 20 millions. 



Xenon equal to 1 part by weight in about 40 millions of 

 air ; by volume, 1 part in 170 millions. 



As before remarked, it is not maintained that all the 

 krypton and all the xenon have been separated ; it is likely, 

 however, that the separation of the xenon was more perfect 

 than that of the krypton. The results are merely brought 

 forward as the result of a careful experiment to quanti- 

 tatively isolate these gases. 



As a quantity of pure krypton, sufficient for determination 

 of density, had been collected, occasion was taken to redeter- 

 mine the density of that gas, with the following result, 

 that the value, compared with = i6, was found to be 4081. 



The atomic weight of krypton would accordingly be 

 8162 ; the mean of former determinations is 81.28. This 

 is in accordance with its position in the periodic table, which 

 lies between bromine, 80, and rubidium, 85. 



" An Inquiry into the Variation of Angles observed in 

 Crystals, especially of Potassium-Alum and Ammonium- 

 Alum." By Prof. H. A. Miers, F.R.S. 



The author has endeavoured to trace the changes of angle 

 upon one and the same crystal during its growth bv measur- 

 ing it at intervals without moving it from the solution in 

 which it is growing. This is accomplished by means of a 

 telescope-goniometer in which the crystal is observed 

 through one side of a rectangular glass trough, and the 

 changes in the inclination of each face are followed by 

 watching the displacements of the image of a collimator 

 slit viewed by reflection in it. 



Examined in this way an octahedron of alum (ammonium 

 or potassium) is found to yield not one but three images 

 from each face ; and closer inspection shows that the crystal 

 is not really an octahedron, but has the form of a very flat 

 triakis octahedron. 



When a growing crystal of alum is watched for several 

 hours or days, it is found that the three images yielded by 

 an apparent octahedron face continually change their posi- 

 tion ; one set fades away and is replaced by another set. 



The images do not move continuously, but per saltum, 

 indicating that the reflecting planes are vicinal faces which 



