Aprils, 1876] 



NATURE 



459 



protection from birds. The effects of changes of temperature 

 Mr. Darwin points out. Hildebrand's and Hanstein's explana- 

 tions of the torsion he thinks inadequate. Darwin's observations 

 prove it resides in the individual awn-cells. When isolated and 

 dried these latter twist on their own axis, similarly in direction, 

 &c., to the awn and with moisture untwist. Finally, this re- 

 markable power is shown to depend on the molecular structure 

 of the twisting cell-walls. Nageli and others' researches into 

 twisting cells have not led hitherto to their importance in plant 

 life,— The Secretary briefly referred t© a technical paper by the 

 Rev. J. M. Crorobie, " On the Lichens of Antarctic America 

 collected by Dr. R. O. Cunningham during the Voyage of 

 H.M.S. Nassau, 1867-9." In this ninety-seven species and 

 varieties are recorded : twenty-four of these and a genus, Endo- 

 cena, are attributed to be new. — A discussion on the potato 

 fungus followed. At the President's request Mr, Carruthers 

 reiterated the salient features of Pro£ de Bary's recent investiga- 

 tions. He called attention to the difference in thickness of the 

 mycelial threads carrying oospores and antheridia, to the septate 

 character of the threads, and to other points collectively adverse 

 to Mr. W. Smith's views of the "resting spore " oi Peranospora ; 

 De Bary believing two fungi have been confoimded. The Rev. 

 M. Berkeley defended Mr. Smith's conclusions as opposed to 

 De Bary's, asserting that as the former, by photographs 

 and drawings from nature, had shown the sexual congress of 

 antheridiimi and oogonium derived from the imequal sized 

 spawn- threads, no reasonable doubt of their connection existed. 

 Admitting De Bary's extensive knowledge of fungi, Mr. 

 Berkeley, nevertheless, objected to his style of criticism. Mr. 

 Smith himself read a long written reply answering De Bary's 

 objections in detail. He averred that Sadebeck's recent obser- 

 vations supported his own as to two sizes of mycelial threads, 

 and the other objections raised with regard to the oogonia and 

 antheridia. As to septal character of the threads, this belongs to 

 Peronosfora, those of Pythium being destitute in this respect He 

 fiirther alluded to the warty bodies of Montagne's Artotrogus, 

 showing De Bary had misconceived their nature. The Stras- 

 bourg professor's animadversion on the life-history of Smith's 

 " rcsting-spore " being yet incomplete is weakened when the 

 former admits it may take a year to resolve, and as yet only nine 

 months have elapsed since the discovery of the bodies in ques- 

 tion. Other remarks pertaining to the "resting- spores" being 

 found in dry leaves, after decay in water, and on perennial my- 

 celium were made, Mr. Smith concluding that De Bary had not 

 entirely comprehended his publications on the subject. Mr. Renny 

 expressed his opinion that the points were not absoutely settled 

 on either side, discrepancies still appearing to him to exist. De 

 Bary's objections were allowable on the ground of his extensive 

 acquaintance with the subject, while possibly Smith may not have 

 given the exact value to what he saw. Mr. T. Dyer suggested 

 that the bodies of the so-called Artotrogus may be but mycelial 

 dilatations, and not true oogonia ; on this ground a fresh investi- 

 gation might be necessary to ascertain its relations to the ques- 

 tions at issue. Mr, A. Murray, Mr, Cooke, and Dr. Masters 

 each made a few remarks. Air. Carruthers, in conclusion, 

 thought Mr. Renny had put the case fairly. De Bary only meant 

 to question Smith's knowledge of the coiudia, not that he was 

 ignorant of the potato fungus ; he, De Bary, may have misunder- 

 stood Smith's drawings, but in the elucidation of facts and truths 

 he certainly could not fairly be accused of hypercriticism, seeing 

 that he himself had carefully watched and studied the develop- 

 ment, mode of hosts, &c., since 1874. 



Geologists' Association, March 3. — Mr. William Car- 

 ruthers, F.R.S., president, in the chair. — On the Bagshot sands ia 

 the Isle of Sheppey, by Major F. Duncan, D.C.L., F.G.S. A 

 recent section, made with the object of lowering a road, has 

 exposed a considerable part of Bagshot sands, colour pale or 

 light yellow, with clay lines, resting on the top of the dark 

 London clay. The distinctive features are absence of green- 

 sands, presence of thin layers and nodules of iron- sandstone, 

 absence of fossils. As there is no discoloration of the sands at 

 the base of the section the author thought they might have been 

 sub-aerial deposits — blown sand ; otherwise he considered that 

 there would have been a shading off between the clays and the 

 lands. This theory, the author thought, might serve to explain 

 the well-known variability of this series. — On some rock frag- 

 ments in the above-described section, by Mr. W. H. Shrubsole. 

 These had t)ecn found 6 to i8 incnes from the surface and were 

 all igneous, except some specimens of hard sparry limestones. 

 After discussing the possibility of these fragments haying been 



brotight to Sheppey by human agency, the author contended 

 that, although their position in the described section may have 

 been due to such a cause, still that they must originally have 

 been conveyed on ice, towards the close of the Glacial epoch, 

 and been stranded whilst Shepp>ey was emerging firom the sea.— 

 Known facts and unknown problems in Arctic geology, by 

 Charles E. De Ranee, F.G.S. , H.M. GeoL Survey. The 

 existing glacial phenomena of the Arctic regions, Greenland, and 

 Spitzbergen, were described, marine shells of existing species 

 occurring at heights of more than i,oc» feet above the sea, and 

 living marine Crustacea in fresh-water lakes elevated many fert 

 above the sea-level in Polaris Bay. The observations on the 

 discoloration of the waters of the Arctic Ocean were dwelt upon, 

 and the bearing on the phenomena observable on the Engli^ 

 Glacial deposits. The crystalline rocks of the north coast of 

 America and the Greenland coasts were referred to the Laa* 

 rentian system, and the whole of this area stated to have been 

 land, during the Lower Silurian epoch- The Upper Silurian, 

 however, was shown to be well represented in all the islands of 

 the Arctic Archipelago, and the "Ursa Stage" of Pro£ Heer, 

 Devonian, or Lower Carboniferous, with coal-seams, to be pre- 

 sent in synclinals in the latter, and also to exist in Spitzbergen 

 and Bear Island, as do the overlying mountain limestones. The 

 Lias and Oolitic rocks of the Arctic Islands, East Greenland, 

 and Spitzbergen were described, and the Cretaceous plant- 

 bearing beds of West Greenland, and their associated coal-seams. 

 The Miocene basalts of Mid-Greenland, vrith their associated 

 plants, were mentioned as probably connected with the basalts 

 of East Greenland, and as ranging to Spitzbergen, 



Physical Society, March 25.— Prof. G, C, Foster, F.R.S., 

 president, in the chair. — The following candidates were elected 

 members of the society : — The Marquis of Salisbury, Prof^ 

 Liversidge, W. Ackroyd, Tolver Preston, W. MerritL — Mr. 

 O. J. Lodge, B.Sc, made a communication on the flow of 

 electricity in a plate, in continuation of a paper which he read 

 before the society on Feb. 26. In order to apply the principle 

 of images already described to the flow of electricity in plates 

 bounded by straight lines, it is necessary that the angles of the 

 plate should be aliquot parts of 180° ; and, since this condition 

 excludes obttise angles, the number of rectilinear figures which 

 can be treated is very limited. They are rectangles, equilateral 

 triangles, two cases of right-angled triangles, the two limiiing cases 

 of the isosceles triangle for wWch the equal angles are o* and 90° 

 respectively, and many cases of the general two-sided polygon or 

 "wedge," including the regular two-sided polygon or "strip." 

 Since the images of a pole in a wedge lie on a circle as in a ka- 

 leidoscope. Cotes' property of the circle may be applied to obtain 

 expressions for the potential of any point, and for the electrical 

 resistance of the plate to the flow from any number of point poles 

 situated anywhere in it. The expressions are rather long, but 

 they become simpler in certain special cases which were pointed 

 out Making the angle of the wedge vanish the expressions 

 modify into corresponding expressions for the strip, the resist- 

 ance expressions of which always contain hyperbolic trigono- 

 metrical iimctions of the positions of the poles. The potential 

 fimctions for a circular sector also follow from a general case of 

 the wedge. The general resistance formula, applied to the case 

 of the isosceles right-angled triangle leads to some continued pro- 

 ducts, all of which are generalisations of Wallis' expressions for 



![ . The product of these products, which is itself of the same 

 2 



form, has been reduced by Mr. J. W. L. Glaisher to the com- 

 plete elliptic int^ral usually denoted by K, its modulus being 

 Sin 45*. This quantity appears in all the resistance expressions 

 for right-angled triangles and squares which the author has yet 

 examined. The case of an equilateral triangle leads to more 

 complex and interesting products, which were reduced by Mr. 

 Glaisher to the product of two theta-fimctions, with Sin 75° as a 

 modulus. When the conditions of flow are laiown in one recti- 

 linear figure they may be extended to a large number of others 

 by alternate processes of reflecting the plate in one of its own 

 boundaries, and of cutting it along one of its straight flow or 

 equipotential lines. Diagrams of such transition figures were 

 sho^^•n. In order to obtain the resistance of a compotmd con- 

 ductor by means of the known resistance of its components, it is 

 necessary that the flow conditions in each component shall 

 remain entirely imaffected by their being connected together. 

 Thus if the resistance of a circuit consisting of two wires side by 

 side is to be deduced from the resistance of the wfres separately, 

 by the ordinary method of adding their conductivities, it is 



