September 21, 1905] 



NA TURE 



507 



sea had the form of a lipped cylinder. Adopting the 

 description given in I. Kings, which differs some- 

 what from that of II. Chronicles, M. Moors has de- 

 duced for the cubic contents of the haih, a measure of 

 capacity frequently met with in the Old Testament, 

 the relation 



I bath = J (Mosaic cubit)''. 



The remainder of the work deals with the system 

 of weights, measures, and coinage in u^e among the 

 Israelites. Carefully disclaiming any bias in ques- 

 tions theological, he adopts the Bible as the chief 

 authority on the subject of which he treats. The 

 weights and measures mentioned in the Bible are not, 

 however, always very clearly defined, and in attempt- 

 ing to combine them in a homogeneous system we 

 are confronted with apparently hopeless incon- 

 sistencies. Owing to this difficulty M. Moors finds 

 it necessary to have recourse to materials of some- 

 what incongruous character. From a strange medley 

 of midwives, manna and mummies, he evolves, with 

 much ingenuity, a series of metric equivalents for the 

 weights and measures of the Israelites. He claims 

 that his equivalents are confirmed by all those 

 passages in the Bible which contain references to 

 weights and measures. It is interesting to note that 

 his value for the length of the cubit, viz. 443-61 milli- 

 inetres, agrees very closely with the value obtained 

 recently by Sir Charles Warren (17-64 inches, = 

 448-05 mm.). 



It is hardly possible to accept the view of M. Moors 

 that the Bible was intended inter alia as a text-book 

 on mensuration. In spite of his laudable effort to 

 throw light on the old Hebrew weights and measures 

 they still remain dim to us. In the region of 

 metrology the Israelites would indeed appear to have 

 baffled the commentator, and to have buried their 

 authoritative standards " deeper than did ever 

 plummet sound " out of the excavator's reach. 



So far as we have checked the numerical calcula- 

 tions made by M. Moors, we have found them in- 

 variably accurate. There is, however, an obvious 

 misprint in the last line of his letterpress; " 43-S " 

 should read "43,500." 



A Primer oit Explosives. By Major A. Cooper-Key, 

 Edited bv Captain J. H. Thompson. Pp. xii4-94- 

 (London : Macmillan and Co., Ltd., 1905.) Price is. 



This little book should prove of great value to those 

 for whose benefit it has been mainly written, viz. the 

 local inspectors under the Explosives Act, and those 

 dealers whose trading necessitates the handling and 

 storage of explosives. 



No one can better realise the want of some little 

 handbook on the subject than H.M. Inspectors, and 

 it is to meet this want that Major Cooper-Key has 

 written this useful book, which, it is pointed out, is 

 "not a treatise on explosives." The author gives a 

 short description of the manufacture of the chief 

 explosives, but its great value will be found in the 

 sections devoted to special risks with each class, the 

 methods of packing and storing, and a particularly 

 useful chapter on the general construction and 

 management of a store, the destruction of explosives, 

 &c. 



It is certain that a careful study of the book by 

 local inspectors will lead to a better understanding of 

 the whole question of explosives and the Act 

 generally, and hence to a more intelligent perform- 

 ance of their responsible duties. For those traders 

 and users who have the handling of these goods after 

 they have left the manufactory the book should be 

 equally valuable, and it should do much to lessen the 

 NO. 1873, VOL. 72] 



risk of those untoward accidents which occur from 

 time to time, generally from ignorance of the proper- 

 ties of the bodies dealt with. J. S. S. B. 

 .4 yote-book of Experimental Mathematics. By C. 



Godfrey and G. M. Bell. Pp. 64. (London : 



Edward Arnold, 1905.) Price 2S. 

 This book gives concise instructions for carrying out 

 a number of simple quantitative e.xperiments in 

 mechanics. It is specially suited for students who 

 intend to sit for Army Entrance Examinations, but 

 the excellence of the course outlined renders the book 

 very serviceable for general use in schools ; the 

 students get accustomed to fundamental methods of 

 measurement, obtain concrete conceptions of elemen- 

 tary science, and secure much data well adapted to 

 serve as examples and illustrations in a course of 

 practical mathematics. The experiments include 

 measurements of lengths, areas, volumes, weights, 

 specific gravities, fluid pressures, forces, moments, 

 velocities, accelerations, and many other physical 

 quantities. A full and careful list is given of the 

 requisite apparatus and fittings, and the book will oe 

 of very great assistance to teachers in the arrange- 

 ment of a thoroughly sound elementary course of 

 experimental science. 



LETTERS TO THE EDITOR. 

 [The Editor does not hold himself responsible for opinions 



expressed by his correspondents. Neither can he undertake 



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



manuscripts intended for this or any other part of Nature. 



No notice is taken of anonymous communications.] 



Cause and Prevention of Dust from Automobiles. 



The article on the above subject in the issue of Nature 

 for September 14 (p. 485) is an important contribution to 

 a subject of great interest and importance to the com- 

 munity, but it contains a statement with reference to 

 tar-macadam which in the interests of engineers should, 

 I think, be verified. Speaking of " Tarmac " the writer 

 says, " the slag is thoroughly impregnated, so that if the 

 pieces are broken further a tarred surface is still found." 



I have examined many specimens of tar-macadam, in- 

 cluding " Tarmac." I have never found any sign of 

 penetration of tar. I am aware that some believe in this 

 alleged penetration, but it seems to be obvious that any 

 material sufficiently porous to enable tar to saturate it 

 would be totally unfit for road-making. 



That tar-macadam, and, of course, "Tarmac," have 

 virtues for motor road-making may be admitted ; but this 

 penetration theory is not the reason, and it is a pity that 

 the myth should still exist, as it tends to prevent the trial 

 of other substances far more suitable for roads than furnace 

 slag. 



The reason why tarred granites and similar hard stones 

 have not hitherto been found so effective is entirely a 

 matter of surface adhesion. Given a suitable tar mixture, 

 there is no reason why hard, non-porous stone should not 

 be as efficient as slag. Penetration has nothing to do 

 with it. J. Vincent Elsden. 



38 St. Stephen's Gardens, Twickenham. 



In reply to Mr. Elsden, I agree that it is of no use 

 to hold mythical views. I think, however, that he is 

 really mistaken in his views that the slag in " Tarmac " 

 is not penetrated by the tar. Possibly it may not be 

 penetrated by the most viscous constituents, but upon 

 examining a broken piece of " Tarmac " I have found that 

 the surface is distinctly darker than that of slag which 

 has not been treated. The difference is very noticeable 

 under the microscope, and if a bit of slag from the interior 

 of a treated portion is heated the tar is readily seen, 

 which fact appears to be conclusive evidence that penetra- 

 tion by the tar takes place. I do not, however, suppose 

 that the penetration is very uniform, as slag is not a very 

 uniform material, and therefore in some parts the effect 

 might not be so evident. W. R. Cooper. 



82 Victoria Street, S.W. 



