August 12, 1922] 



NA TURE 



\2Q 



account of a polyzoon, PJumatella longigemmis, which 

 occurred in the artificial lake whence Colombo obtains 

 its water, and formed a continuous coating on the 

 walls of the wash-water tank at the filtration works. 

 Shorter notes deal with a new species of LycEenid 

 butterfly (Arhopala orfnistoni), with Lepidoptera of 

 economic interest in Ceylon, and with the stridulation 

 of a leaf-insect. 



Surface Temperatures in the North Sea and 

 in German Lakes. — The International Council for 

 Marine Investigations has just issued a Bulletin 

 Hydrographique (June 1922) containing a summary of 

 all the observations of surface temperature in the 

 North Sea during the years 1905-1914. There are 

 more than 200,000 measurements made from com- 

 mercial vessels and they are tabulated as means 

 during each ten-day period for the mean year, and 

 for areas of one degree of latitude and longitude, or 

 for one-half degree, in each case. The results are 

 represented graphically by a series of charts, one for 

 each ten-day period. These show in a striking 

 manner the " flow " of the isothermal boundaries 

 throughout the year. A very interesting study of 

 the temperature of the water at the surface of various 

 lakes in Germany has been made by A. Merz ( 1 7< - 

 offentlich. Instituts fur Meereskunde, Berlin, N.F. A., 

 Heft 5, 1920). A specially constructed thermometer 

 was used. The bulb was a vessel of 1 sq. mm. 

 cross-section and 12 cms. long ; the capillar}- stem 

 was 15 cms. in length and was bent at right angles 

 to the elongated bulb. Thus it was possible to explore 

 the water at depths varying by 1 mm. down to about 

 no mm. The results are quite remarkable: on 

 very calm days, when there is no vertical disturbance 

 of the water, the temperature may vary from about 

 21 C. at the surface, to about 8° C. at a depth of 

 about 100 mm. Probably these results will have 

 much significance. 



Meteorology at Hong-Kong. — The report for 

 the year 1921 of the Director, Mr. T. F. Claxton, 

 of the Royal Observatory, Hong-Kong, has just been 

 issued. A heavy rainfall occurred from April 27 

 to July 6, a period of 71 days, rain falling on 59 

 days and yielding 59 inches, or 61 per cent, of 

 the total fall for the year. From September 9 

 to the end of the year, a period of 113 days, the rain- 

 fall amounted only to one inch. The total rainfall 

 for the year was 97-34 in. and the average for the 

 past 38 years is 84-62 in. The greatest rainfall in a 

 day was 6-o6 in. and the greatest in one hour was 

 3-25 in. The highest shade temperature was 92° 

 on August 22 ; the highest in the past 38 years is 97 . 

 The lowest temperature was 44 on February 4, and 

 the lowest for the 38 years is 32°. The maximum 

 wind velocity for one hour was 51 miles ; the 

 maximum for one hour in the past 38 years is 10S 

 miles. The maximum squall velocity in 192 1 was 

 at the rate of 69 miles an hour. There were 21 

 typhoons during the year and the tracks of these 

 are given in the Monthly Meteorological Bulletin for 

 December 1921. In addition to meteorological 

 observations kept at about 40 stations in China, 

 meteorological logs were received from 168 ships 

 operating in the Far East, the latter being used for 

 verifying typhoon tracks. 



Interferometers. — Because of the high degree of 

 accuracy obtainable, interferometric methods of 

 measurement are of extreme value in physical re- 

 search. The application of such methods has been 

 rendered easily practicable by the various Hilger 

 interferometers, which are specialised developments 

 of the Michelson interferometer. The manufacturers, 



Messrs. Adam Hilger, Ltd., 73a Camden Road, N.W.r, 

 now include a list of these instruments in their 

 catalogue and have issued separate booklets de- 

 scribing them. The prism interferometer, the lens 

 interferometer No. 1, and the camera lens interfero- 

 meter (described in Nature, July 14, 1921) are fairly 

 well known and are used in connexion with various 

 physical problems. A simple and compact form of 

 instrument known as the " interferoscope " is now- also 

 available, by means of which the degree of parallelism 

 of surfaces of transparent plates can be determined 

 with more ease and rapidity and with greater accuracy 

 than by micrometer measurement. Minute differ- 

 ences in the thicknesses of opaque parts, e.g. steel 

 thickness gauges, plug gauges, balls for bearings, etc., 

 can also be conveniently measured by placing three 

 of the parts between two glass surface plates and 

 measuring the lack of parallelism in the separation 

 of the plates. As the accuracy obtainable with this 

 instrument is about one-millionth of an inch it should 

 form a valuable test-room tool as well as a physical 

 laboratory instrument. 



Chemical Composition of the Earth's Crust. — 

 Prof. W. Vernadsky of the Radium Institute, Petro- 

 grad, writing from the Paris Museum d'histoire 

 naturelle, says it has been shown by Oddo and 

 Harkins that the outer shell of the earth's crust, down 

 to a depth of about 10 miles, consists predominantly 

 of elements with even atomic numbers, but he believes 

 that it is now possible to go further than this, and 

 that it can be shown that the elements of different 

 atomic numbers can be grouped according to the part 

 they play in the economy of the earth's crust as 

 follows : 1. Cyclic (biogenic) elements. — These consti- 

 tute 99-6 per cent, of the mass of the earth's crust, 

 and 86-4 per cent, of them are elements with even 

 atomic numbers. These elements enter into the com- 

 position of organisms, and the chemical changes they 

 undergo are cvclic. They include the following 28 

 elements : Ag,' Al, As, B, Ba, C, Ca, CI, Cu, Fe, F, 

 H, K, Mg, Mn, N, Na, Ni, O, P, Pb, S, Si, Sn, Sr, 

 Ti, V, and Zn ; and probably also the following 10 

 elements : Bi, Cd, Co, Cr, Hg, Mo, Sb, Se, Te, and W. 

 2. Inert gases. — These have all even atomic numbers. 

 They are chemically inert. They include A, He, Ne, 

 Kr, and Xe. 3. Elements of the rare earths. — These 

 include Ce, Dy, Er, Eu, Gd, La, Lu, Nd, Pr, Sa, 

 Tb, Tin, Yb. It is characteristic of these elements 

 that they take no part in the formation of vadose 

 minerals. 4. Radioactive elements. — These include 

 Ac, Nt, Po, Ra, Th, and U. They are genetically 

 related to uranium and thorium and are subject to 

 disintegration. 5. Inert metals. — These include An, 

 Ir, Os, Pd, Pt, Rh, and Ru. They do not give vadose 

 minerals. 6. Diffused elements. — These include I 

 Cs, Ga, In, I, Li. Rb, Sc, and Tl. It is a marked 

 characteristic of these elements that they show very 

 little tendency to form minerals, although their atoms 

 are widely diffused through the rocks of the earth's 

 crust. All the elements of this group have odd 

 atomic numbers. Prof. Vernadsky points out that 

 the chemical processes going on in the earth's crust 

 are closely dependent upon the atomic constitution 

 of the matter of the crust. A portion of this is always 

 in an active state, and is, under present conditions, 

 to be regarded as a store of free energy ; e.g. those 

 cyclic elements that undergo changes through the 

 influence of radiant solar energy, and those radio- 

 active elements which give a continual display of 

 atomic energy. So long as these sources of energy 

 are maintained, chemical changes will proceed in the 

 earth's crust as at piesent ; but the equilibrium is 

 slowly changing, partly through dissipation and partly 

 through the disintegration of the radioactive elements. 



NO. 2754, VOL. I io] 



