March 15, 1888] 



NA TURE 



461 



been carefully brought up to the level of recent researches. 

 The methods of the separation of active principles, such 

 as morphine and atropine, from the crude substances, 

 and their reactions, are not given. 



Prof. Bentley does not undertake to give more than the 

 most general indication of the action of the remedies he 

 has so fully described. All that is said of rhubarb, for 

 instance, under the heading of medicinal action, is that 

 "it possesses tonic and slightly astringent properties, and 

 in large doses it acts as a purgative." This is a very good 

 system for pharmaceutical students, and according to 

 some authorities for medical students also at the com- 

 mencement of their career. But it manifestly encourages 

 learning by rote. What impression of definiteness or 

 value does the word " tonic," for example, represent in 

 the mind of the juvenile reader.? Of course none. 



Again, whilst we acknowledge that Prof. Bentley has 

 on the whole confined himself to an account of the actions 

 of the various drugs on the healthy organism, we must 

 object to the heading" Medicinal Properties," which is put 

 before the paragraphs descriptive of these. A drug has 

 an action quite apart from the circumstance that it may 

 be employed as a " medicine," i.e. in relation to the treat- 

 ment of disease. 



The book contains a number of beautiful illustrations 

 of plants and drugs. It is remarkably free from typo- 

 graphical errors, and the style of its production reflects 

 credit on the publishers. 



Catalogue of the Fossil Mamtnalia in the British Museum 

 {Natural History). Part V., containing the Group 

 Tillodontia, the Orders Sirenia, Cetacea, Edentata, 

 Marsupialia, Monotremata ; and a Supplement. By 

 •Richard Lydekker, B.A., &c. (London : Printed by 

 order of the Trustees, 1887.) 



With this part Mr. Lydekker completes his laborious 

 and very meritorious work of cataloguing the large col- 

 lections of Mammalian fossil remains in the British 

 Museum. 



The named species are 719 in number, and are arranged 

 under 301 generic and 100 family headings, 106 out of 

 this total being regarded as not to be distinguished from 

 existing forms. 



Rich as is the collection in the British Museum, it is 

 very far from including all the known existing fossil forms 

 of Mammalia ; but, failing any treatise on such, this work 

 will be of the greatest assistance to all workers in this 

 field. Though at the commencement of his Catalogue 

 Mr. Lydekker did not give descriptions of all the forms 

 detailed, yet, as it proceeded, he somewhat altered his 

 method, giving some of the more important distinctive 

 characters, and so the value of the work to the student 

 has been increased. 



A volume of this nature is not capable of being de- 

 scribed in any detail, and it will suffice to add that it will 

 be quite a necessary book of reference in the library of a 

 biologist. 



Lehrbuch der Histologie. Von Dr. Philipp Stohr, a. o. 

 Professor der Anatomie zu Wurzburg. (Jena : Gustav 

 Fischer, 1887.) 



This is an excellent little treatise on the same lines as 

 Ranvier's larger "Traits Technique d'Histologie " and 

 Prof. Schafer's smaller " Essentials of Histology." The 

 various tissues are systematically described with clear and 

 well selected wood-cut illustrations ; and after each section 

 of the systematic description a full and careful account is 

 given of the best methodsof preparation, which will enable 

 the student to verify the descriptive account. The micro- 

 scopic structure of the chief organs is treated in the same 

 way. The directions as to technique are not merely 

 those suitable for an elementary student, but such as will 

 be useful to one who is advancing in the direction of 



original research. The figures are, with the exception of 

 a few diagrams, actual representations of what the student 

 should be able to obtain by the particular mode of pre- 

 paration recommended. An introductory chapter treats 

 of the arrangement of the laboratory, and the apparatus 

 and reagents necessary. E. R. L. 



A Treatise on Photography. By Captain Abney, 

 RE., F.R.S. (London: Longmans, Green, and Co., 



1888.) 



The appearance of a fifth edition of this well-known book 

 is sufficient proof of its popularity, and no trouble seems to 

 have been spared by the author to make this issue a 

 success. The volume has been thoroughly revised, and 

 much new matter added. The author gives the results of 

 his researches, communicated to the Royal Society, on 

 the " Effect of the Spectrum on the Haloid Salts of 

 Silver ; " concluding with a chapter on celestial photo- 

 graphy, and photography with the microscope. 



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 

 <^ Nature. No notice is taken of anonymous communi- 

 cations.^ . 



Coral Formations. 



I HAVE read Captain Wharton's paper on "Coral Forma- 

 tions " (p. 393), and the letters of Mr. John Murray and Mr. G. 

 C. Bourne in your issue of March i. 



There is, doubtless, room for difference of opinion as to this 

 important and many-sided question, but I think the balance of 

 evidence is in favour of Mr. Murray's view as to the formation 

 of lagoons. 



In this connection the fact that carbonate of lime is soluble in 

 water had been practically overlooked, and its increased solu- 

 bility in sea-water seems to have been unnoticed before Mr. 

 Murray formulated his views as to their formation. The active 

 life in coral reefs is practically outwards (assuming a shape 

 similar to fairy rings on grass), leaving the central portion 

 more or less dead, or with wide spaces of coral sand and only 

 scattered patches of living animals. The organic matter in 

 this dead coral, by its oxidation, produces carbonic acid, 

 which dissolving in the sea-water exalts its solvent action 

 on the carbonate of lime, now more or less in an amorphous 

 condition. 



Reducing such a question to figures has a great advantage, 

 and is often the only way of arriving at a safe conclusion. 

 With assistance derived from the Scottish Marine Station, I 

 have lately been conducting some experiments on the solubility 

 of carbonate of lime in sea-water, the results of which may 

 interest the readers of Nature at the present time. 



The experiments were conducted with sea-water of specific 

 gravity i 0265 (obtained from the German Ocean 20 miles 

 from land), and at temperatures of from 70° F. to 80° F., 

 which reefs require. The corals used were several species of 

 Porites. 



Dead or rotten coral exposed to sea-water under these circum- 

 stances is soluble to the extent of 5 to 20 ounces per ton. 



Take now a reef with a lagoon already formed, half a 

 mile in diameter. This will give an area of about 600,000 

 square yards, and supposing the water to be 3 feet deep 

 and only one-sixth part of this to be in actual contact with 

 the dead coral, we have 100,000 tons exerting its solvent action. 

 This would give, were the sixth part of the lagoon water to be 

 expelled and replaced with fresh sea-water at each tide, and 

 taking the solvent action at only 10 ounces to each ton, an 

 amount of carbonate of lime removed equal to about 3000 

 tons each year. 



I do not insist that such an amount of carbonate of lime must 

 year by year be removed from the lagoon, but I think these 

 experiments show that the carbonate of lime so removed may 

 easily exceed any additions to the lagoon by secretions of 



