January 20, 1921] 



NATURE 



^11 



of material for the study of these artiodactyls, 

 especially in Lower Miocene strata, and their peculiar 

 limitation to American deposits render the diagram 

 of their evolution useful to students of the mammalia. 



Bulletin 663 of the U.S. Geological Survey on 

 ■■ The Structural and Ornamental Stones of Minne- 

 sota," by Oliver Bowles, is effectively illustrated with 

 coloured plates of polished specimens — a method of 

 imparting information that in our islands has, we 

 think, been left to private enterprise. \ publication of 

 this kind is obviously a distinct service to a community 

 that also contributes liberally to research in the so- 

 called '• purer " branches of geology. 



Some broad features of Hawaiian petrology are 

 dealt with by S. Powers in the American Jotirncd of 

 Science (vol. I., p. 256, 1920). The olivine nodules 

 in the basalts are regarded as early products of 

 differentiation brought up from lower levels, and the 

 occasional trachytes that are described seem to be 

 due to differentiation in local volcanoes after their 

 connection with the main subterranean cauldron had 

 been cut off. Useful maps are given of several of 

 the islands. 



Atte.ntion may be directed to a very convenient 

 glossary of the economic mineral productions of the 

 United States published by the U.S. Geological Survey 

 under the title of " Useful Minerals of the United 

 States," Bulletin 624, a revision of Bulletin 585. This 

 consists of two parts — the first a geographical index, 

 in which the various States of the Union are given 

 in alphabetical order, and under each the most im- 

 portant mineral productions of that State, also alpha- 

 betically arranged. The second part consists of a list 

 of the names of sortie six hundred minerals in 

 alphabetical sequence, in which the composition and 

 general uses of each are given briefly, together with a 

 list of the States in which it occurs in important quafi- 

 fitii'S or in some noteworthy form. The work thus 

 forms a very convenient index to the mineral produc- 

 tion of the United States, and it would be a very great 

 'Ivantagc if all important mining countries published 

 i^ts on similar lines. The suggestion might with 

 j^rr at advantage be followed by our Imperial Mineral 

 K»-sourres Bureau. 



LivERi-ooL Observat(>r\ m liidston. under tfie 

 lirectorship of Mr. W. V.. I'luriimor, hIs issued its 

 port for the years 1917-19, which is published by 

 I Ik; Mersey Docks and Harbour Board. It has not 

 I'l-en found possible to issue annual reports as was 

 lie custom prior to the war. The signal-gun for time, 

 liich is for definite nautical purposes, was fired, 

 ithout alteration for summer time, one hour after 

 ' ireenwich mean noon. Seismological observations 

 are regularly re<-ordcd, and in the tables published 

 notes arc made respecting the different phases. Tem- 

 perature records in the reports arc from thermometers 

 mounted on the north side of the observatory; in 

 former >ears, when observations were made from 

 Kitruments mounted on the south side, the results 

 ive too high a reading. There were 76 days in 1917 

 ith no sunshine, 68 days in 1918, and 68 days in 

 ,\<). For *ind velocity it is still assumed that the 

 locity of the wind is three times greater than that 

 ! the cups of the Robinson anemometer, although 

 NO. 2673, VOL. 106] 



this factor is recognised as too large. The detailed 

 daily meteorological observations are most complete, 

 and a summary is given for the several months and 

 for the year. The number of hours that the different 

 winds blew during each day affords very useful in- 

 formation and is of great interest as associated with 

 the varying character of the weather. There is much 

 that can be followed with advantage at other sub- 

 sidiary observatories. 



\'oL. XIV. of the Collected Researches of the 

 National Physical Laboratory extends to more than 

 300 pages, and is devoted entirely to optics. Its 

 characteristic feature is the aid it affords to the 

 manufacturer of optical instruments, and of telescopes 

 in particular. One of the fifteen papers reprinted is 

 devoted to a description of the methods adopted at the 

 Laboratory for the calculation of telescope objectives, 

 and a second gives the corrections to the curvatures 

 of the lenses of an objective when the glass of a new 

 melt is not quite identical in refractive index with 

 the glass previously used. Charts for assisting in 

 the selection of suitable glasses for cemented doublets 

 are given, and those cases in which the curvatures 

 do not allow a doublet to be cemented are met by 

 the substitution of a cemented triplet. In a paper 

 devoted to refractometers of the critical-angle type, 

 such as are used in commercial testing, it is pointed 

 out how extensive the powers of these instruments 

 are and how the actual instruments have in the past 

 fallen short of the accuracy possible owing to 

 mechanical defects. Modifications of the original 

 Zeiss form of construction are suggested which, when 

 the instrument is used with the proper precautions, 

 should raise the accuracy considerably. 



.\ MARKED degree of red sensitiveness in some 

 "ordinary" gelatino-brornide plates was observed and 

 recorded many yiears ago; it seems possible that the 

 key to this unexpected result has been found by Mr. 

 F. F. Renwick, who contributes a paper on "The 

 •Action of Soluble Iodides on Photographic Plates " 

 to the January issue of the Journal of the Royal 

 Photographic Society. Mr. Renwick finds that by 

 treating a plate for a few seconds with a very dilute 

 solution of potassium iodide there is really no 

 fog«'ng effect (as Dr. S. E. Sheppard stated about 

 a year ago), but that the plate is rendered markedly 

 orange and red sensitive. This he demonstrates by 

 bathing an ordinary plate for from 15 to 60 seconds 

 in a I in 20,000 potassium iodide solution, washing 

 it with water and exposing it to a spectrum. This 

 appears to be the first instance recorded of a colour- 

 less solution conferring colour sensitiveness. Mr. 

 Renwick has tried a fair number of different salts, 

 but so far has discovered only one other that acts 

 similarly. Sodium or pot.-issium cyanide in solution 

 of a strength of one in from 2000 to 10,000 gives an 

 exactly similar effect. The author leaves a theoretical 

 discussion of these results to a future occasion. 



Thr investigation of soap solutions by Dr. McBain 

 and his students at the University of Bristol has been 

 continued by the demonstration that aqueous .sodium 

 oleate at temperatures between 0° C. and 25° C. can 

 exist in any one of thror- forms ■ , |i m ciily liquid 



