Nov. 29, 1888] 



NATURE 



lOI 



first contributed, by Dr. Thorell's labours, for the 

 )Iy of works on the spider-fauna of exotic regions : 

 less his extensive work, " Studi sui Ragni Malesi e 

 Juani,'"' in three vohimes, 1877-81, describing and 

 "Tecording over five hundred species of the spiders of 

 that richest of all known exotic regions, the Malay Archi- 

 pelago. Up to the time of the publication of the present 

 lume, but few Ikirman spiders were known, the earliest 

 \\\g an Epeirid, described by the late Dr. Stoliczka in 

 10)9. This was followed, in 1878, by two others recorded 

 by Mr. T. Workman, of Belfast ; eight more were re- 

 corded in 1 88 1 in Dr. Thorell's work above mentioned 

 (on the spiders of the Malay Archipelago) ; and finally, 

 twenty-two more by M. Eugene Simon in 1884. The 

 total number of species of Burmese Araneidea now known 

 is 163, by far the larger portion being new to science. 

 Dr. Thorell records 145 species, of which 90 are new to 

 science, and 130 new to Burmah. These figures doubtless 

 give a very meagre idea of the ?piders of such a rich 

 zoological district as the Burmese Empire. Not to mention 

 its situation in the tropics, Burmah has much in common 

 with the productions of China, Siam, India, and the 

 Malay Archipelago. We may therefore safely hazard a 

 conjecture that the figures given by Dr. Thorell can 

 scarcely represent a twentieth part of the spiders of 

 Burmah. It is to be hoped that since the — still compara- 

 tively few — species as yet known have been collated in the 

 present work, an impetus will be given to natural history 

 collectors to add to our knowledge. Vox the want of figures 

 in Dr. Thorell's work there is some compensation in the 

 concise diagnoses which head each lengthened descrip- 

 I lion. Excepting the introduction, which is in Italian, the 

 work is written m Latin. It is exceedingly well got up, 

 forming a handsome volume of over 400 pages, and is 

 dedicated to the Rev. O. P. Cambridge, General A. W. 

 I M. Van Hasselt, and Dr. Ludwig Koch. The greater 

 part of the Burmese spiders described by Dr. Thorell 

 were collected by Signor Leonardo Fea, mostly in Upper 

 (or North) Burmah ; and of the rest some were collected 

 in its southern and some in its central districts. 



O. P. Cambridge. 



An Introduction to Practical Inon^anic Chemistry. J3y 



Wm. Jago, F.C.S., F.I.C. (London : Longmans, 1888.) 



This volume of 72 pages is chiefly taken from the author's 



" Inorganic Chemistry, Theoretical and Practical," and 



has been separately issued by request. It is doubtless 



,, sufficiently exact for students who are preparing them- 



|i selves for the " growing number of examinations in which 



[ the practical analysis of one or more simple salts is 



I required," and therefore presumably it will serve the end 



I for which it was designed ; but it contains many state- 



!i ments that would tend to confuse the genuine student, and 



give his teacher unnecessary trouble. For instance, on 



p. 15 it is stated that a " brown ppt. of SnS " is soluble in . 



"SAm^,, re-pptd. by HCl"; and a little lower down that 



"Arsenic, arsenious compounds . . . Heated in tube— all 



salts sublime." Both of these statements have so slender 



a foundation in fact that their direct tendency is to deceive 



the student. These are mere examples that might be 



multiplied considerably. Towards the end of the book, 



tables are given for the " E.xamination of Mixtures," and 



wherein they differ from the methods in common use they 



do not appear to be improvements upon them. 



LETTERS TO THE EDITOR. 

 \The Editor does not hold himself responsible for opinions 

 expressed by his correspondents. Neither can he under- 

 take to return, or to correspond with the writers of, 

 rejected manuscripts intended for this or any other part 

 of Natvrk. No notice is taken of anonymous communi- 

 cations. ^ 



Engineers versus " Professors and College Men." 

 Some of your readers may recollect that last year (Nature, 

 vol. XXXV. p. 462) I was led to put the following question to the 



.£"«^'«^«-.— "What is the result of dividing 10 eggs per mimite 

 by 2 eggs? Would it, or would it not, be 5 eggs per minute " ? 

 T-> this I have not yet received an answer ! It must be very 

 difficult ! . ^ 



I ventured to put the question because the Engineer had (in a 

 leading article !) asserted that the result of dividing 3,942,400 

 foot-pounds per minute, by 33,000 foot-pounds, is 1194 horse- 

 power. It had actually accused me of ignorance for pointing out 

 the error of .«uch a statement ! 



But even this remarkable dictum is outstripped in absurdity by 

 some of the Engineer s more recent assertions. I quote only a 

 few, any one of which would be sufficient for my present pur- 

 pose, leaving the vast storehouse to be fully ransacked by other 

 inquirers more curious, and less busy, than myself. 



On the loth of August last the readers of the Engineer were 

 treated to the following ex cathedra pronouncement : — 



" . . . it is almost impossible to point to anything of value in 

 trade, or manufactures, or engineering which has emanated from 

 the highly-trained Professor or College man." 



No comment whatever need be made on this. 



A fortnight later, in reviewing a book on the steam-engine, 

 the Engineer remarks of Carnot's principle : — 



"... it will soon be understood that with steam this is not 

 true. . . ." 



There is nothing in the context to qiialify this assertion, rather 

 there is much to intensify and aggravate it. There is mani- 

 festly a confusion between temperature and pressure ; but it is 

 difficult to find its exact nature ; and the only at all analogous 

 case that I can remember is embodied in the indignant outburst 

 of a Celtic student, hard pressed in an "oral," "D'ye mane 

 to till me, Sor, that wather boils at a hundthred degrees in 

 Oireland?" 



It might well be thought that we had now gauged the maximum 

 of possible absurdity. I3ut, on September 28, the Engineer under- 

 took to enlighten its readers on the subject of Energy ; and the 

 effort resulted in some astounding information. 



Speaking of " the equation E = (a form which will, 



perhaps, please my friend Prof. Greenhill, though to me it seems 

 to denote merely the prodiict of a mass by a length) our instructor 

 says : — 



" The received idea is that, so long as we get E equal to a 

 given number of foot- pounds, it is of no consequence whether we 

 vary jy or vary M, . . . but if we introduce the element Time, 

 which ought not to be left out\i\\e italics are mine]. . . . The word 

 Energy is unfortunately very vague. ..." I shall pre-ently 

 recur to this. 



October 5 is not without its little novelty. For, as we are 

 gravely informed, 



" That much despised faculty, common-sense, has always told 

 engineers that when a given volume of air is passed through a 

 channel or trunk, its pressure will fall as the trunk augments in 

 dimensions." 



Even the despised scientific man knows better than that ! : — 

 but, true to his convictions, the .£';/^'-/«fVr ia:nores the conclusions 

 of such mere " Professors and College men " as Bernoulli, Willis, 

 and Sir W. Thomson. 



A week later, commenting on some sensible protests (which it 

 prints, in order to refute (?) them) against its marvellous ideas 

 about Energy, the Engineer gets back to something like last 

 year's confusion, and mixes up work and horse-power in a 

 manner truly amazing. This peculiar phase of his own mind 

 is what the Engin:er designates as the "vagueness" of the 

 word Energy ! 



But the crowning feat is to come. In a very sensible and able 

 introductory lecture to his engineering class at Leeds, Prof. Barr 

 took occasion to speak of the advantages of preliminary scientific 

 training for engineering students, and protested against the 

 mischievous doctrines too often expressed by so-called "prac- 

 tical men" and their literary champions. He took the opportunity 

 of giving a much needed warning against the inaccuracies of the 

 Engineer ; referrirg (among others) to that already quoted about 

 the failure of the Second Law of Thermodynamics. 



He has had his reward ! His difference of opinion from the 

 Engineer is, of course, to be ascribed to youth, inexperience, 

 want of breadth of knowledge, &c. The Engineer gees so far as 

 to suggest such ugly ideas as " disregard for truth " ; and, having 

 done so, immediately proceeds to quote me by name as the author 

 of a statement which, with the utmost possible dibtinctress, I 

 had ascribed to its true author, the late Clerk-Maxwell. 



Prof. Barr is quite able to hold his own against such ant- 



