December 30, 19 15] 



NATURE 



479 



s, and a list of industries which have adopted 

 tintometer. Mr. Lovibond tells us also that 

 our is "a determinable property of matter, and 

 purpose is to make known methods of colour 

 alysis and synthesis which have proved of 

 eat practical value in establishing- standards 

 purity in some industries." "The purpose is 

 to show that the methods (tintometer?) are 

 roughly scientific in theory and practice," and 

 that "a new law (the law of specific colour 

 velopment) has been developed." This is a new 

 me for well-known observational results, 

 he first chapter has some introductory re- 

 rks, and there is a pag-e and a quarter (with 

 coloured plate) devoted to what is headed 

 ast " (colour) "theories." This does not give 

 any novel matter, nor does it contain any 

 criticism of the six theories which he enumerates. 

 Chapter ii. is the most interesting of all, as it 

 relates to the "evolution " of the tintometer. The 

 tintometer is an admirable instrument for regis- 

 tering the colours of objects, opaque or trans- 

 parent, which do not show pure colours. Its prin- 

 ciple is to match such colour illuminated by white 

 light by sending^ a beam of the same white light 

 through one or more red, yellow, blue, and 

 neutral-tinted glasses on to a white screen having 

 various depths of colour till the colour of the 

 object is matched. The choice of the glasses, 

 and the skill with which Mr. Lovibond ground 

 them to give the varying depths of colour which 

 he required, approaches to the marvellous. His 

 method of regaining his standard tints if lost is 

 ingenious, so that observations made with the 

 same quality of white light will always give the 

 same results. The one weak point is the choice 

 of the white daylight used, which is light from a 

 north sky, that, of course, can vary in quality 

 from day to day. A recognised standard of 

 artificial light would be better. 



I Mr. Lovibond rather fights shy of the spectrum, 

 d has given no results of matches to the band 

 spectrum colours by the absorption method. 

 le spectrum throughout its length is unmatch- 

 le by this method. 

 When he makes statements regarding- . the 

 ipctrum analysis he sometimes gets out of his 

 pth. He tells us that there is one red ray in 

 B spectrum between A and B which cannot 

 absorbed, and that this (red) energy has never 

 ueen investigated " as a separate form of spectrum 

 red." Mr. Lovibond should look to the absorp- 

 tion by his glasses. 



The book has its value when the theory part 

 is left out, and may serve as a practical guide to 

 "tintometry " through the useful examples which 

 are shown in its later chapters. 

 NO. 2409, VOL. 96] 



OUR BOOKSHELF. 

 Field Analysis of Minerals for the Prospector, 



Miriing Engineer, Traveller, and Student. By 



G. D. McGrigor. Pp. 86. (London: The 



Mining Magazine, 191 5.) Price 35. 6d. net. 

 The methods of mineral determination here 

 advocated by the author have been found useful 

 by him as a prospector beyond the reach of 

 laboratories. He has no doubt observed that a 

 student who has passed through an ordinary 

 course of chemistry is still poorly equipped for 

 dealing with natural chemical compounds as they 

 are presented to him in the field. In some col- 

 leges, however, the chemical curriculum includes 

 a course in practical mineralogy, in which field 

 conditions are, so far as possible, reproduced. 

 Even Mr. McGrigor 's book will not do away with 

 the desirability of a sound course of inorganic 

 chemistry as a prelude to such work as he marks 

 out, and few will agree that this foundation should 

 involve only " a very short period of instruction. " 

 The student of chemistry, for instance, will know 

 that when Mr. McGrigor speaks of substances con- 

 taining sulphur on p. 13, he means sulphides, 

 and that there are also such things as sulphates ; 

 he will note the slip on p. 12, where the weight 

 in air divided by the weight in water is said to 

 give the specific gravity of a substance ; and he 

 will know (p. 19) that the oxidising flame does 

 not "impart" oxygen to the material under ex- 

 amination. Possibly he will never have used 

 microcosmic salt, and this is just where the author 

 might have helped him (p. 22), by pointings out 

 cases where it provides conclusive tests, instead 

 of suggesting that it gives the same results as 

 borax. Sir Warington Smyth is cited as the 

 authority for some of these statements; but the 

 author's practice must have led him somewhat 

 farther. 



The reactions described in the systematic 

 portion usefully include those of tellurium, van- 

 adium, osmium, and tantalum, which are omitted 

 in many treatises. A just balance of simple wet 

 tests and ordinary blowpipe-tests is indicated. 

 The use of some good text-book on mineralogy 

 is very properly recommended, especially Brush 

 and Penfield's "Manual of Determinative 

 Mineralogy," to which Mr. McGrigor 's book 

 may well serve as a pocket introduction. 



G. A. J. C. 

 Egypt of the Egyptians. By W. Lawrence Balls. 



Pp. xvi-f-266. (London: Sir Isaac Pitman and 



Sons, Ltd., 191 5.) Price 6^. net. 

 Mr. Lawrence Balls not only knows Egypt of 

 the modern Egyptians, but during his years of 

 residence there he bore his part in adding to her 

 material prosperity. Indeed, he writes with au- 

 thority on the problems of cotton cultivation, and 

 while applying himself to their solution he formed 

 opinions upon many other subjects connected 

 with the country. This book is the result of such 

 study and observation on the spot, and it is well 

 worthy of study in its turn. 



The chapters on the Nile, on irrigation, and 

 the crops are perhaps its most valuable sections, 



