i86 



NATURE 



[Jan. 7, 1875 



valuable, especially if the irrelevant matter is reduced 

 to a minimum. The small book before us contains a 

 carefully compiled and accurate digest of many of the 

 most prominent facts of human physiology, with inci- 

 dental references to some of the best known peculiarities 

 of a few of the lower animals, illustrated by several appro- 

 priate and well-selected diagrams, among which, how- 

 ever, there is an important one indicating the general 

 distribution of the arterial system, which is unfortunately 

 reversed, and another explaining the leverages of the 

 body, representing a man as standing with his centre of 

 gravity far in front of the tips of his toes. The language 

 employed is clear and concise, whilst many of the best 

 known terms in common use among physiologists are 

 explained in a glossary at the end of the book. Some of 

 the practical illustrations suggested to the pupil for his 

 own instruction are particularly to the point. There are 

 some explanations with which, however, we cannot agree, 

 such as that the activity of the circulation of the blood 

 which accompanies physical exercise is the result of the 

 alternate compression and relaxation of the veins ; and 

 that a much vaunted theory as to the cause of cholera, 

 which involves the purchase of a much advertised appa- 

 ratus for its relief, has sufficient foundation for even the 

 slightest mention in any book for the use of students. 

 The non-technical character of the work will commend 

 it to many as a useful introduction to physiology. 



The Gardener'' s Year Book and Almanack, 1875. By 

 Robert Hogg, LL.D., F.L.S. {Journal of Horticulture 

 Office.) 

 This is a very handy and valuable little book. The in- 

 formation it contains is of a kind that may be thoroughly 

 depended upon. ]5esides a great deal of practical infor- 

 mation of a miscellaneous sort, there are tolerably copious 

 gardening directions for each month, besides selected lists 

 of fruits and vegetables, and of the new plants of last year. 

 It will be very useful to amateur gardeners, and would be 

 still more so if it gave some short and plain descriptions 

 of various horticultural operations— such, for example, as 

 pruning different kinds of fruit-trees. 



LETTERS TO THE EDITOR 



YTlie Editor docs not hold himself resfonsiMe for opinions expressed 

 ln> his correspondents. N'either can he undertake to return, 

 or to correspond zuitli the ivriters of, rejected manuscripts. 

 No notice is taken of anonymous communications.^ 

 Absence of Microscopic Calcareous Organic Remains 

 in Marine Strata charged with Siliceous Ones 

 In a letter headed "Deep-Sea Researches," and subscribed 

 "W. C. Williamson, Owens College," in your issue of the 24th 

 Dec. (vol. xi. p. 148), the author, after having stated that Dr. 

 Wyville Thomson has come to the conclusion that the calcareous 

 Globigerinx and other such elements had been removed by the 

 "solvent action of carbonic acid accumulated in the deep-sea 

 waters," adds that, " In my memoir [1847, op. i/V.] I arrived at 

 the same conclusion." 



Then follow extracts from the " Memoir " itself, alluding to 

 the removal of all the calcareous forms, leaving only the siliceous 

 structures," by " carbonic acid gas in solution in water." 



Finally, the author states :— "After venturing upon these con- 

 clusions in 1S47, not as mere speculative guesses, but as the 

 deliberate result of a Icng series of investigations carefully 

 worked out, I need scarcely say how intense was the interest witli 

 which I read Dr. Wyville Thomson's observations, v/hich so 

 thoroughly sustain and confirm the accuracy of mine. My con- 

 clusions were wholly derived from the microscopic observa- 

 tions of earths and rock specimens which I compared with the 

 few examples of foraminiftrous ooze with which I was then 

 familiar." 



"Felix qui potuit rerum cognoscere causas." 

 In enumerating the diffti'ent kinds of destruction which take 

 place in sponge-spicules generally, I have noted that the cal- 

 careous spicule is subject to one in particular, "in which there 

 is a general breakdown of the whole fabric, which gradually 



becomes resolved into a group of aqueous-looking globules, of 

 different sizes,' among which there is not a trace of the original 

 structure to be seen. Were this change confined to those cal- 

 careous spicules which I have mounted in Canada balsam, I 

 should have inferred that it was caused by the balsam ; but I find 

 that the same change accompanies these spicules where they 

 may have been taken in by the kerataceous sponges to form an 

 axis for their horny fibre ; and it is worthy of remark that the 

 spicules of the Echinodermata, which may lie side by side with 

 them, do not appear to be similarly affected. Of what nature 

 the origin of this disorganisation may be I am ignorant ; it is a 

 chemical question ; but the destruction takes place so rapidly in 

 many instances that I have for some time past ceased to mount 

 any more calcareous spicules, and now preserve a record of them 

 by immediate sketches." (Ann. and Mag. of Nat. History, vol. xii. 



1S73. P- 457-) 



Thus it follows that a removal or an anniliilation of the forms 

 of these microscopic calcareous organisms takes place after they 

 have been repeatedly washed in fresh water, dried under a great 

 heat, and covered at the same time with balsam, that is, treated 

 artificially ; as well as naturally, when they are mixed up with 

 other microscopic organisms to form the core of the horny fibre 

 of marine sponges ; while the same thing takes place with the 

 Foraminifera, as testified by slides, in some of which fragments 

 of Operculina arabica mounted upwards of twenty years ago have 

 nearly all passed into dissolution, and others in which the 

 spicules of calcareous sponges which were mounted not more 

 than six years since have disappeared altogether, leaving 

 nothing but a few aqueous-looking globules in their places re- 

 spectively. 



So that this dissolution may arise without the presence of 

 " carbonic acid g is in solution in water ; " and as it is common 

 to the calcareous organisms mounted in balsam for tlie cabinet, 

 as well as in the core of horny fibre in the marine sponges of the 

 " deep-sea," we may fairly assume that the removal of the cal- 

 careous forms from the siliceous ones in marine deposits may be 

 due to more causes than that assigned by the author of the letter 

 to which I have alluded. 



Moreover, even the siliceous spicules which form the core of 

 the glassy fibre in the vitreous sponges may, with the circum- 

 jacent layers of tlie fibre itself, undergo absorption to such an 

 extent, in the skeleton of these sponges, aftir death, as to leave 

 nothing but a siliceous shell with hollow, continuous tube 

 throughout. 



Such are the results of my microscopic observations among 

 these minute organism^:, and therefore, in the concluding words 

 of the letter under reference, "I think I am justified in wishing 

 the fact to be placed on record." 



Indeed, so common and rapid is the process of destruction or 

 inherent disintegration among the microscopic calcareous organ- 

 isms which I have mentioned, that I am compelled to the con- 

 clusion that it is to this chielly, and not to " carbonic acid gas 

 in solution in water," that we must look for a satisfactory ex- 

 planation of the fact that minute calcareous organic forms are 

 comparatively absent among the siliceous ones of marine de- 

 posits, both recent and fossilised. 



The agency of decay is as difficult to comprehend as the 

 agency ot development (why we should die any more than why 

 we should live) ; hence it becomes unphilosophical to limit the 

 operations of either to any one process. All that appears certain 

 in the matter is, that the three great attributes of the system, 

 viz.; creation, preservation, and destruction, form a cycle in 

 whicii, to speak figuratively, the words "perpetual change" 

 may be enwreathed. Henry J. Carter 



Budleigh-Salterton, Dec. 26, 1874 



The Constant Currents in the Air and the Sea 



The riiilosophual ATaqazine for July, August, and .September 

 contains a memoir, continued through the several numbers, by 

 Baron N. Schilling, Captain in the Imperial Russian Navy, on 

 " the Constant Currents of the Air and the Sea." It appears that 

 this memoir was first published in the Russian, afterw.rrds in the 

 German, and finally translated and published in the English 

 language ; so that it seems to be regarded as a memoir of con- 

 siderable importance. 



When any new andj extraordinary results are obtained in any 

 department of important scientific inquiry, the interests of science 

 require that the basis of these results should be critically exa- 

 mined before they are received ; and this is especially, so where, 



