2/8 



NA TURE 



[January 22, 190^ 



instead of increasing it. In the investigation, account is taken 

 of the dependency of the coefficient of friction on the velocity 

 based upon experimental determinations. 



Some estimates of the stresses in the riveted attachments in 

 ships are given in the December number of the Transactions of 

 1 he Institution of Engineers an I Shipbuilders in Scotland by 

 Dr. I. Bruhn. Taking ships of various dimensions, the author 

 calculates the stresses at the gunwale amidships from the ordinary 

 theory of beniing, and the stresses in the rivets are obtained from 

 the assumption that the stress is increased above that on the 

 solid plate in proportion to the reduced sectional area. By 

 drawing curves showing the relation between the stresses so 

 calculated and the lengths of the ships, it is shown how the 

 stresses on the edge riveting are being rapidly increased by the 

 increase in the size of vessels and also by the tendency to let 

 full-formed vessels proceed to sea in light or comparatively light 

 c mditions, particularly when water ballast has been added, 

 l'ractically the only way of reducing the stresses is by increased 

 rivet area. In some cases, this may be obtained by closing up 

 the spacing of the rivets, but eventually, as the size of the ship 

 increases, an additional row of rivets must be fitted. 



An interesting report on the plasticity of clays is presented to 

 the Bulletin de la Sociiti £ Encouragement for November 30, 

 1902, by M. B. Zschokke. Of the various theories of plasticity, 

 the author attaches much importance to that of A. Rejto, 

 according to which the peculiar properties of clay are due in the 

 miin to the fact that the cohesion of its particles exceeds the 

 internal friction. A number of experiments are described in 

 which the tenacity of various samples of clay was tested by 

 submitting cylinders to longitudinal traction. One remarkable 

 result of these experiments is that the elongation previous to 

 rupture is greater when the traction is applied rapidly than when 



it is applied slowly. 

 With rapid tractions, 

 the diagrams ob- 

 tained show that the 

 separated portions 

 taper to sharp, al- 

 most conical, points 

 (Fig. 1), whereas with 

 tractions applied 

 gradually to the same 

 samples of clay the 

 breakage seems to 

 lake place abruptly 

 before the constric- 

 tion at the middle of 

 Fig. 1 Fig. -•. the bar has become 



great (Fig. 2). This 

 remarkable property is the exact opposite of that met with 

 in the majority of substances, such as metals. The attempt 

 to explain the phenomena has led M. Zschokke to a study 

 of the microscopic structure of different samples of clay, in 

 illustration of which several diagrams are given. Finally, the 

 author defines plasticity as that property of a body, possessing 

 as great a cohesion as possible, of undeigoing, under the action 

 of external forces, very great permanent deformations without 

 the deformed body exhibiting any change in its cohesion rela- 

 tively to the original body. Plasticity, it is pointed out, 

 depends largely on the absorbing power of the clay and its 

 attraction for the absorbed water, and the latter depends partly 

 on the size of the particles and partly on the physical or chemical 

 affinity between these particles and the water. 



The Annates de V Observatoire Aslronomique of Moscow 

 (vol. iv., second series), which is published under the direction 



NO. 1734, VOL. 67] 



of Prof. W. Ceraski, contains some valuable contributions to 

 astronomy. The volume opens with the reductions of the 

 meridian observations made by M. Modestow of stars in the 

 zone 0° to +4° declination, the object being to determine the 

 positions of all stars down to magnitude S. This is followed by 

 three contributions by 11. S. Blakjo on the calculation of 

 occultation of stars by the moon, containing tables to facilitate 

 reduction, observations of the Leonids in 1S97, 1S9S and 1899, 

 and of the planet Mars in 1S96-1S97 (with plates). Prof. 

 Ceraski gives a valuable photometric s.udy of a certain number 

 of stars in the constellation of Coma Berenices, and adds a 

 process plate showing a portion of the region. 



Mi:. II. A. Bryden contributes to the Fortnigktly Review 

 for January an article on the decline and fall of the South 

 African elephant. It appears that the wild elephant has now 

 practically ceased to exist south of the Cunene and Zambesi 

 rivers. About the year 1S30, elephant hunting in Cape Colony 

 was prohibited by the British Government. Since that time, 

 remaining herds have been carefully protected, and they still roam 

 the dense iungles of the Knysna Forest and the Addo Bush in 

 large numbers. It is a curious illustration of what a little 

 timely preservation will do for wild creatures that often within 

 a few- miles of Port Elizabeth and Mitenhage there are strong 

 troops of these animals, while one may travel elsewhere fifteen 

 hundred miles up country and not succeed in finding a single 

 wild elephant. 



In his recent report on the trade of Wiirtemberg for the year 

 1901 and part of 1902, Dr. F. Rose, H.M. Consul at Stuttgart, 

 refers to the heavy fall in the price of carbolic acid owing to the 

 manufacture of this substance by a synthetic process. The 

 commencement of the manufacture of synthetic carbolic acid in 

 Germany was, the report points out, the direct result of the 

 prohibition of the export of carbolic acid from the United 

 Kingdom in January, 1900. In a former report, Dr. Rose, in 

 the course of some remarks on the production of synthetic car- 

 bolic acid, said that " the high prices for phenol, caused by the 

 prohibition and the low price of benzol in Germany, were 

 instrumental in giving a great impetus to the endeavours of 

 German chemists to discover a cheap working method of pre- 

 paring phenol synthetically from benzol, and thus rendering 

 Germany independent of the export from the United Kingdom. 

 The danger to the British export trade of carbolic acid then 

 foreshadowed has now become an actual fact." 



In a reprint of a pamphlet from the Humane Review en- 

 titled " The F'ate of the Fur-Seal," the author, Mr. J. Collinson, 

 directs attention to the cruelties connected with the driving and 

 slaughter of these animals on the PribilofTs, as well as to the 

 evils of pelagic sealing. 



A recent fasciculus (No. 1310) of the Proceedings of the 

 U.S. National Museum is devoted to materials for a mono- 

 graph of the North American insects of the order Thysanoptera. 

 At the conclusion of the memoir, the author, Mr. W. E. Hinds, 

 discusses the phylogeny of the different sections of the group. 



We have received a copy of a second lecture on " Thorough- 

 breds and their Grassland," by the Rev. E. A. Woodruffe- 

 Peacock, forming No. 2 of the Rural Studies Series, in which 

 the nature of soils and the best kinds of grass with which to 

 sow them are discussed. 



The American Naturalist for December contains an im- 

 portant paper, by Prof. A. W. Grabau, on the morphology and 

 growth of the gastropod shell, with especial reference to the 

 protoconch, or embryo-shell. Attention is called to the fact 

 that several of the modern limpet-like shells, such as Acmaea 

 and Crepidula, have coiled protoconchs, whence it is inferred 

 that this type of shell is probably not, as might at first sight 



