344 



NATURE 



[August i i, 1898 



author uses the term " Gummidruck" (printing by means 

 of india-rubber), he is careful enough to point out that 

 other means besides india-rubber are now employed. 

 The process, which is here very clearly described, is 

 accompanied by many wrinkles which will be useful to 

 those who have never previously employed it. 



Perhaps few amateurs would attempt this method of 

 printing, considering the numerous other more simple 

 means in use, but professionals will find that a great 

 latitude can be obtained in development, so that the 

 appearance of the picture can be made to suit various 

 tastes. 



A short and interesting historical notice is given showing 

 how the process has gradually been evolved, and this is 

 followed by an account of the advantages of the method, 

 the materials employed, and the whole manipulation. 



Chapter Vii. describes briefly the three-colour and 

 combination pigment printing, while Chapter viii. con- 

 tains a summary of the process. Two plates, which 

 accompany the te.xt, illustrate the difference between the 

 simple- and combination-gummidruck. 



Text-Book of Physical Chemistry. By Clarence L. 

 Speyers. Pp. vii + 224. (New York : D. van Nostrand 

 Company. London : E. and F. N. Spon, Ltd., 1898.) 



Beginning with a chapter on energetics, in which 

 Ostwald is followed, the author treats in order the 

 properties of gases, thermodynamics, physical change 

 including the properties of solutions, chemical equi- 

 librium and chemical change, Gibbs' phase rule, the 

 effect of temperature on chemical change, and electro- 

 chemistry. A satisfactory feature is the free use of the 

 calculus. The book is intended for students ; under 

 these circumstances the omission of all reference to 

 original papers is, we think, a serious mistake. The 

 method adopted is to give the theory of a phenomenon 

 in mathematical form, following this up by a number of 

 exercises illustrating the equation obtained. The exer- 

 cises appear to be taken, as a rule, from the original 

 memoirs dealing with the subject under consideration, and 

 are doubtless useful ; but in many cases the deduction of 

 the equation is too much abbreviated to be easily 

 followed, and the experimental basis of the theory is 

 nowhere sufficiently fully considered. This tendency 

 to put theory before experiment is especially objectionable 

 in teaching. 



The treatment from the standpoint of energetics, 

 adopted in the opening chapters, is not strikingly suc- 

 cessful. The following statement occurs, for example, 

 on p. 18; "When we attempt to get work from the 

 volume energy of a gas, we find that the work we get 

 comes from heat energy, or some other energy, and that 

 so long as the gas remains a perfect gas and its mass 

 does not change so long the volume energy of the gas 

 remains constant., whether T changes or not." The 

 volume energy of a perfect gas is, however, given by the 

 product of its volume and pressure, and is therefore 

 proportional to the absolute temperature. 



The author's view (p. 20), that " The kinetic theory is 

 a troublesome thing and is becoming an object of 

 ridicule," will hardly meet with universal acceptance. 



Notwithstanding the faults above mentioned, it is only 

 fair to add that the book is up to date, and that the range 

 of subjects considered is wider than usual. 



Recueil de Donnees Numeriques Optique. By H. Dufet. 

 Premier Fascicule. Pp. ix4-4i5. (Paris: Gauthier- 

 Villars et Fils, 1898.) 



Both chemists and physicists will be much indebted to 

 the French Physical Society for the valuable and useful 

 volumes which they are now publishing. The one before 

 us, which is devoted to wave-lengths, and indices of gases 

 and liquids, contains a mass of data, which have been 



NO. 1502, VOL. 58] 



collected from far and near, and brought together in a 

 compact and serviceable form. 



Great value must be attached to the volume, as refer- 

 ences are given in every case ; and even though the 

 work is not quite complete, it is a most desirable addition 

 to every chemical and physical library. 



The preparation of the data here collected must have 

 entailed a great amount of work, and M. Dufet deserves 

 the thanks of scientific men for completing the present 

 volume. 



LETTERS _ TO THE EDITOR 



[ The Editor does not hold himself responsible for opinions eX' 

 pressed 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 covtnninicatioits.l 



Solar Halos. 



There is a coloured halo at a considerable angular distance 

 from the sun that is a very usual phenomenon in {e.g.) the 

 Engadine in winter. Its angular diameter appears to be the 

 same as that of the distant white halo sometimes seen round the 

 moon. 



On July 2 we were ascending the Fiirgen Pass from the Breuil 

 side, and such a coloured halo was visible. The snow slope and 

 ridge in the front of us cut off the lower part of this halo ; but 

 it was completed both in colour and form by reflection off the 

 snow. Thus the coloured circle was complete ; but the upper 

 part (more than half, of course) appeared "in the air," the 

 lower part " on the snow." 



The surface of the snow was unusually sparkling in ap- 

 pearance. 



It may be of interest to record that, when I have been at a 

 considerable height (over 6000 feet above the sea at the least), 

 and there have been very fine cirrus clouds close to the sun, I 

 have seen exceedingly pure colours not arranged in rings. Thus 

 I have seen, in a cloud, a very delicate rose-crimson entirely 

 surrounded by a very pure green. With more continuous mist 

 or cloud between me and the sun, I have seen a succession of 

 coloured rings round the sun ; and I have seen these vanish and 

 give place to the single coloured halo of large diameter referred 

 to earlier. 



In the Engadine in winter I once saw a very complicated 

 arrangement of circles and parhelia ; but it would be impossible 

 to describe these without a figure. I have such a figure, and 

 could lend it to any one specially interested in the subject. 



5 Keppel Place, Devonport. W. Larden. 



A Living Toad in a Snake. 



I SHOULD be obliged by your inserting the follovving ex- 

 perience if you think it remarkable. 



Yesterday we killed an adder (?) here, about 38 inches long ; 

 and seeing that he had made a meal evidently some little time 

 before, out of curiosity we opened him, and extracted a large 

 toad, which was about half-way down the snake's interior, or 

 about 18 inches. 



The toad, whose head was much wider than the snake's, and 

 whose body was many times as large as his enemy's head, we of 

 course all thought must be dead ; and we laid him on a flower- 

 bed, wondering how he could have got inside the snake at all, 

 for it certainly seemed a case of the greater being contained in 

 the less. Of course we knew the marvellous stretching powers 

 of a snake's jaws, but this seemed to eclipse them all. 



As we watched the toad he seemed to move, so we bethought 

 ourselves of trying to revive him, and, after pouring water freely 

 over him, and whisky and water down his throat, we were 

 intensely astonished to see him revive ; so much so that he 

 stood up on all-fours, blown out like a balloon, and made a 

 kind of a dart at a stick in the most comical way. 



Eventually "Jonah," as we promptly christened him, dis- 

 appeared amongst the flowers. Can any of your readers quote 

 a like case of resuscitation ? Perhaps some of them might be 

 able to afford information as to the probable duration of the 

 toad's entombment. F. W. Major. 



Woodlands, Bettws-y-coed, N. Wales, August 2. 



