148 



NA TURE 



YDec. 18, 1884 



OUR BOOK SHELF 

 On the Healthy Manufacture of Bread. A Memoir on 

 the System of Dr. Dauglish. By Benjamin Ward 

 Richardson, M.D., F.R.S. (London : Bailliere, Tyn- 

 dall, and Cox, 18S4.) 

 THIS pamphlet is another of Dr. Richardson's labours in 

 the cause of public health. It deals mainly, as the title 

 implies, with healthy bread, and especially with the sys- 

 tem of the late Dr. Dauglish of Malvern for baking what 

 is now generally known as aerated bread. The advan- 

 tages of the aerated process are stated by the author 

 to be that the destructive influence of fermentation is 

 prevented. There is no chemical decomposition of the 

 flour whatever, and therefore no loss of material, while 

 the rising of the dough is just as effectively carried out. 

 The aerated bread contains, therefore, all the gluten and 

 all the albuminous food of the wheat, out of which the 

 living' tissues are constructed, as well as the food which 

 ministers to the animal warmth and vital activity. More- 

 over, much labour to the baker is spared, and the knead- 

 ing by hand is wholly dispensed with — a matter of some 

 consideration to delicate or fastidious persons. The 

 gradual steps by which the process has been worked out, 

 from the incubation of the idea in the brain of Dr. 

 Dauglish to the modern aerated process of baking are 

 fully traced by Dr. Richardson, who describes also the 

 different effects of fermentation and aeration on the 

 different qualities of flour, the economic and sanitary 

 advantages of the new system to the workmen (by no 

 means the least important part of the subject, as those 

 who recollect Mr. Lakeman's report on the London 

 bakeries, and who read Chapter IX. of this little work, 

 will acknowledge), and the public advantages of the 

 aerated bread in relation to health. An appendix con- 

 tains a brief memoir of Dr. Dauglish. 



Proceedings of the Edinburgh Mathematical Society. 

 Second Session, 1883-84. 



OUR readers have seen from time to time in our "Society" 

 Notices the titles of papers read before this young .but 

 from the outset vigorous body, and must have often 

 wished for a more intimate acquaintance with their con- 

 tents (as the odoriferous steam issuing from the cookshop 

 tempts the hungry " Arab " to enter and feed). We are 

 glad to find, from the volume before us, that the Society 

 is in a position to print its Proceedings, for we now know 

 how interesting the papers are. They are not, like some 

 other papers nearer home, caviare to the general, but 

 they deal with matters which come home to every mathe- 

 matical teacher. Mr. Mackay writes on the circles asso- 

 ciated with the triangle, viewed from their centres of 

 similitude ; Mr. Muir, on the condensation of a special 

 continuant ; Dr. Macfarlane, on voting ; Prof. Chrystal, 

 on an application of matrices to spherical geometry, on a 

 problem in partition of numbers, &c. Mr. Allardice fur- 

 nishes some useful notes on spherical geometry and 

 trigonometry ; Mr. Browning, some illustrations of har- 

 monic section ; Mr. Barclay, notes on the teaching of 

 elementary geometry (abstract only), and Mr. Traill, 

 proofs of the theorems as far as " Euclid" i. 32, from 

 first principles. Other papers are : a good concise ac- 

 count of Pascal's " Essais pour les Coniques" by Mr. 

 Macdonald ; the hypothesis of Le Bel and Van't Hoff, 

 by Prof. Crum Brown ; on the representation of the 

 physical properties of substances by means of surfaces, 

 by Mr. Peddie ; and a joint account of the problem 

 " La Tour d'Hanoi " (one of displacements), by Messrs. 

 Allardice and Fraser. With these Proceedings are bound 

 up Prof Taifs introductory address on Listing's " Topo- 

 logie," which, our readers will remember, has been pub- 

 lished in the Philosophical Magazine (January 18S4, pp. 

 30-46, with plates), and Mr. Muir's Presidential Address 

 entitled " The Promotion of Research ; with Special 



Reference to the Present State of the Scottish Univer- 

 sities and Secondary Schools " (delivered February 8, 

 1884). 



Elementary Text-Book of Trigonometry. By R. H. 



Pinkerton, B.A. (London : Biackie and Son, 1884.) 

 This elementary text-book of 176 pages contains all the 

 essentials for obtaining a knowledge of trigonometry 

 proper. It might be used either by those who desire 

 merely a thorough grounding in the elements, or, as a 

 first book, by those who intend to take a full analytical 

 course. The arrangement is good, the text well written, 

 and the examples, worked and unworked, are numerous 

 and judiciously chosen. The introductory chapter on the 

 measurement of angles is particularly commendable. We 

 should prefer, however, not to write " 7r/3 radians " but 

 " 7r/3 radian," reading it "//'-thirds of a radian." It may 

 be suggested also to a writer who has the courage to 

 introduce reforms, whether the time has not come for 

 dispensing with the so-called tablogsines, tablogcosines, 

 Sec, and using only logsines, logcosines, &c. Tabular 

 log functions are, according to our experience, well-meant 

 aids which only hinder. 



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. 

 No notice is taken of anonymous communications . 

 [ The Editor urgently requests correspondents to keep their letters 

 as short as possible. The pressure on his space is so great 

 that it is impossible otherwise to insure the appearance even 

 of communications containing interesting and novel facts .] 



Iridescent Clouds 



On Thursday evening, December n, about fifteen minutes after 

 sunset, in the south-west direction as seen from the Royal Obser- 

 vatory here, were two rather large clouds about 10° or 12° high, 

 and below them several much smaller ones, all of them of tile 

 most brilliantly iridescent colours and nothing but bright colour, 

 of a kind I do not remember to have seen before, though they 

 were not improbably like some described by several of Nature's 

 correspondents last year. 



The principal cloud, some 5° or 6° long and 2° or 3 across, 

 exhibited a diagonal band of glowing green, passing through 

 blue into exquisite violet on either side, while it was fringed 

 nearly all round by dull red. 



The second largest cloud, a little below and rather to the east- 

 ward of the first, exhibited all the same colours in similar diagonal 

 bands, but unconformably with the places of the bands of the 

 first produced down to it ; though both may have had their bands 

 at right angles to a ray from the sun long since set, but directed 

 on their centres. The sky behind them and all around was 

 singularly dark and sombre, so that these iridescent clouds, in 

 the brightness and richness of their colouring, reminded one 

 more of mother-of-pearl inlaid in a black tea-tray than any 

 ordinary sunset sky. 



The smaller clouds of the same kind lower down gradually 

 lost the central green band and passed into yellow and orange, 

 but were still phenomenally bright specks of luminous material 

 on the dark general background. All this towards the south- 

 west ; while west and north-west the sky was nearly clear, and 

 exhibited, in a sunset-illumined sky "proper," a fairly tin 

 quite ordinary set of thin cirro-stratus rolls of cloud, warmly 

 coloured on one side and cold-gray shaded on the other, like any 

 corporeal body in the same exposure. 



Lower down still on the horizon was a heavy cumulo-stratus 

 cloud, which the west wind presently brought up to eclipse the 

 green and blue iridescent clouds, proving that they were higher 

 than it, though not so high as the dark cirrus haze to the south- 

 west that had served so well to set forth their brilliant and 

 unusual colouring. C. Piazzi-Smytii 



Edinburgh, December 13 



A striking phenomena, apparently a new phase of the 

 cloud-glows, was widely witnessed here on the 13th, and 1 

 myself noticed it, though on a much less scale, and in the north- 



