April 30, 1903 J 



NA TURE 



609 



Science and Art elementary paper is contained on p. 73 

 under the heading of " How to construct chemical 

 equations." The expression " two thicknesses of blue 

 glass " might be more explicit, and the same may be 

 said of the term " injurious " applied to an excess of 

 barium chloride. Many of the pages are unnumbered, 

 and there are numerous misprints. J. B. C. 



Elements of Physics. By Ernest J. Andrews and 

 H. N. Howland ; to which is added a Manual of 

 Experiments. Pp. xi + 386 + 53. (New York: The 

 Macmillan Company; London: Macmillan and Co., 

 Ltd., 1903.) Price 6s. 



The aim of the writers has been to present an account 

 of physics suitable for secondary schools. With this 

 aim in view, they have avoided everything of a purely 

 academic character — with the exception of " little bits 

 of history " which they make a point of inserting. 

 The book is of a very elementary character, and is 

 almost completely free from any mathematics except 

 the simplest arithmetic. More attention is paid to a 

 delivery of the facts with which a pupil is expected to 

 be acquainted than with formal proofs of the relations 

 between them. The authors' methods may be indi- 

 cated by the constant recurrence of the two phrases 

 "it is evident" and "just as." The latter phrase 

 shows the reliance placed on the method of analogy; 

 the former phrase sometimes mean- it is easily proved 

 by simple experiments — and suitable experiments are 

 then described ; sometimes it appears to be used merely 

 to help over a difficult point. Great emphasis is laid 

 on a pupil learning a thing by observation, and this 

 is as it should be. An adequate course of introductory 

 experiments is given in the " Manual." 



In general, the explanations given are clear and 

 sufficiently accurate. It is true that the man who is 

 clothed with the love of accuracy as with a garment 

 will not take much pleasure therein. But there is a 

 rapidly growing class of students — the product of 

 county scholarships, &c. — who, owing to imperfect 

 mental training, require knowledge to be served up 

 in a simple if even somewhat loose way ; and these 

 requirements deserve to be satisfied. 



In a few places there are unfortunate slips. The 

 reference to " permeability " on p. 183 is quite mis- 

 leading — it is confused with " retentivity." Again, 

 in connection with the liquefaction of gases, it is 

 explained how a little liquid air may liquefy a lot; this 

 savours of the monthly magazines. These misconcep- 

 tions should be cleared up in a future edition. 



First Steps in Photo-Micrography. By F. Martin 

 Duncan. Pp. 104. (London : Hazell, Watson and 

 Viney, Ltd., 1902.) Price is. net. 



This little work is intended, as its title implies, to be 

 a guide for those who are beginners in a fascinating 

 branch of photography. It is avowedly written for 

 photographers, and not for microscopists, so that much 

 that is passed over may be excused. The apparatus 

 stated to be necessary is such that good work may be 

 accomplished even with moderately high power-. 



The tendency has been of late to advise beginners 

 to attempt some photomicrographic work with the 

 most meagre appliances, thereby increasing their 

 difficulties at the beginning. 



It is satisfactory to note that in this little book 

 simple yet efficient appliances are advised. The 

 portion devoted to the illumination of objects, perhaps 

 the most important part of the whole subject, is treated 

 all too briefly, but in other respects the book may be 

 recommended to those who are commencing photo- 

 micrography, as a useful guide which will materially 

 assi-t them in their earliest efforts. 



LETTERS TO THE EDITOR. 



I'll.' Editor does not hold himself responsible for opinions 

 expressed by his correspondents. Neither con lie undertake 

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

 manuscripts intended for Hits or any other part of NaT'JRE. 

 No notice is taken of anonymous communications.] 



Radio-active Gas from Well Water. 



I have recently found that water from deep wells in 

 Cambridge contains a radio-active gas, and I am anxious 

 to see whether water from other sources possesses the same 

 property. I should be greatly obliged if any of your readers 

 who have access to deep level water would fill a clean two- 

 gallon can with it and forward it to the Cavendish Labor- 

 atory. I should, of course, pay the carriage and return the 

 can. I may say that I have already had samples of water 

 from Birmingham and Ipswich, each of which contained the 



1 J.J. Thomson. 



Cavendish Laboratory, Cambridge, April 25. 



Can Dogs Reason ? 



Dr. Hill has recently asked the question, " Can dogs 

 reason?" The following analogy has always appeared to 

 me to be a sufficient reply. In ordinary circumstances, tew 

 human beings make use of their sense of smell; to excite 

 it, the odour must be fairly strong, and also unusual. It 

 may be regarded as probable that few dogs make habitual 

 use of any power of inference, but have only vague sensory 

 impressions, to which an almost automatic response is given. 

 Yet under sufficient stimulus, they may perform acts in- 

 volving an exertion of a considerable amount of " thought." 

 Whereas, then, dogs rarely " think," but frequently make 

 use of their delicate sense of smell, human beings seldom 

 make use of that sense, but constantly exercise their reason- 

 ing faculties. 



Again, is not the opening of a box somewhat akin to the 

 exercise of an inventive faculty? Teach a man how to 

 operate a complicated machine of which he does not under- 

 stand the mechanism, and it may be doubted whether he 

 will connect the process of setting it in motion with some 

 desire to gain an advantage which is not obviously attained 

 by doing so. 



I am tempted to describe an occurrence which reveals 

 in a dog which I have at present the possession of two 

 rather rare qualities of mind for a dog. One is the accumu- 

 lation of brightly coloured objects. This dog sleeps on a 

 mat in a basket. On taking out the mat to clean it, a 

 strange collection of articles is generally neatly arranged 

 below it ; I remember, for instance, large pieces of red seal- 

 ing-wax attached to strings, a comb, a piece of whalebone, 

 a Brussels sprout, some lumps of coal showing pyrites, a 

 polished dry rib bone, some kindling sticks with resin, &c. 

 These objects had not been gnawed, but merely placed under 

 the mat as valued possessions. 



Again, this dog has a keen sense of a joke. Some days 

 ago, a small dog with a loose chain was wandering in the 

 garden. Its owner came out and called it. My dog caught 

 the chain, dragged the little dog away, and waited events. 

 As soon as the owner approached, the small dog was dragged 

 out of reach, and it was not until after a long chase that 

 the little dog was captured. These small incidents show, I 

 think, that it is as impossible to classify all dogs together 

 as it is to classify human beings : their minds naturally run 

 in very different directions, and, just as there are inventive 

 or artistic men, so dogs may show leanings towards speciat 

 developments of their minds. William Ramsay. 



NO 1748, VOL. 67] 



Bullfinch and Canary. 



That a bullfinch can be trained to pipe a whole tune, or 

 more, to perfection, that is to say, do it, so far as intonation 

 and rhythm are concerned, as well as any skilled musician, 

 everybody knows. It is also a fact, though perhaps less 

 common, that a canary, placed in an adjoining room and 

 hearing the tune of such a piping bullfinch over and over 

 again, may, quite by himself, i.e. without being trained for 

 it, acquire the same accomplishment to the minutest detail. 



An experience, however, which I have had during ,■> 



