November i8, 1897] 



NATURE 



71 



and implying discontinuity, was to be distrusted, for there was 

 no such thing as discontinuity in the problem. In any case, an 

 empirical formula should have a very simple form. Mr. Rose- 

 Innes admitted that a formula founded on sound hypothesis was 

 to be preferred to empirical expressions. But mathematicians 

 had not yet provided an hypothesis applicable to a substance 

 whose molecular arrangement was so complicated as that of ether. 

 Mathematicians must, therefore, improve their methods before 

 working formulae could be deduced from their hypotheses. The 

 use of an empirical formula with five constants was justified by 

 Kepler for the planetary orbits. Kepler used that formula with 

 no other justification than his experience that an ellipse fitted his 

 observations better than a circle. Similar instances might be 

 cited from recent work on the theory of solution, and osmetics. 

 Mr. Johnstone Stoney was disposed to look for a mathe- 

 matical cause for the cusp ; it was improbable that the physical 

 change was so abrupt as that represented graphically by the 

 author. The question might be tested by plotting the two curves 

 y = z'"» and j/ = a v^, and by observing whether these also sug- 

 gested discontinuity. — Mr. W. L. Waters then read a paper on 

 the variations in the E.M.F. of the H-form of Clark cells 

 with temperature. The authors, Messrs. F. S. Spiers, F. 

 Twyman, and W. L. Waters, have investigated how nearly the 

 true E.M.F. of Clark cells can be computed at different tem- 

 peratures by applying the ordinary temperature correction. 

 As a standard, two cells of the Muirhead type are 

 employed. The four cells under test could be put 

 through cycles of temperature in a special heating bath, 

 containing oil circulated by a centrifugal pumping vane. 

 E.M.F.s were determined by a potentiometer method, and 

 a careful study was made of the "lag" of E.M.F. behind 

 temperature. The results are given in the form of curves. It 

 is shown that " lag," in the H-form of cell, is less than in the 

 "Board of Trade" form. Under ordinary conditions, when 

 the rate of variation of temperature is less than 2° C. per hour, 

 by applying temperature-corrections the true E.M.F. of the H- 

 form can be found to within a ten-thousandth of a volt. In this 

 respect there is little to choose between the H-form and the 

 "Muirhead" cell. Mr. W. R. Cooper thought the authors 

 did not express the case clearly. The E.M.F. of the "Board 

 of Trade" cell could not, with reason, be itself stated within 

 I per cent. But in some cases when, for instance, cells were 

 used differentially, greater accuracy might be required, as, for 

 instance, when a constant source of E.M.F. was being compared 

 with the variations of another source. Here it might be neces- 

 sary to know the " lag." He would like to know with what 

 degree of accuracy the E.M.F. of the standard cell was deter- 

 mined by the authors. The lag that occurred in the "Board of 

 Trade " cell was probably due to diffusion, crystallisation, and 

 solution. — Mr. Waters said the E.M.F. of the standard was 

 measured by a Kelvin balance to one in ten-thousand. 



Entomological Society, November 3. — Mr. R. Trimen, 

 F.R.S., President, in the chair. — Mr. Selwyn Image was elected 

 a Fellow of the Society. — Mr. J. J. Walker exhibited specimens 

 of Anisolabis annidipes, Luc, an introduced species of earwig 

 taken among bones at the chemical works at Queenborough, 

 and of Brachysoimis hirtus. Boh., a rare weevil, taken among 

 dead leaves at Chatham. — Mr. Janson exhibited a variety of 

 Melanargia galaiea of a clear yellowish cream colour, without 

 trace of the usual black markings. It was captured between 

 Dover and Walmer in 1843, ^'^d w^s still in very perfect con- 

 dition. — Lord Dormer showed a remarkable openwork cocoon 

 of an unknown Japanese moth, constructed from the larval 

 hairs. — Mr. Jacoby exhibited fine examples of both sexes of the 

 Australian Hepialids, Charagria ramsayi, C. spleiidens and 

 Hepiahis daphnandri. — Mrs. Nicholl exhibited a selection from 

 the butterflies collected by her this year, in June and July, in 

 the Albarracin Mountains in Aragon, containing several addi- 

 tions to the list of the district published in Madrid by Don 

 Zapater and Herr Max Korb. The species of greatest interest 

 were Erebia zapateri, Oberth., Canonympha iphioides, Staud., 

 Satyriis prieiiri, Pier. , and its fulvous 9 var. uhagoni, which 

 was observed to be much more attractive to the males than the 

 normal form was ; Argynnis hecate, Esp. , and Fainassius 

 apolh, L., of which a female variety occurred with red-centred 

 ocelli on the upperside of the forewing. — The Rev. H. S. 

 Gorham showed examples of the following rare beetles from 

 the New Forest : Notiuphilus ttifipes, Velleius dilatatus, Trich- 

 onyx sulcicollis, and Lytla vesuatoria. — Mr. Tutt showed a 

 series of Noctu^e, taken at Romford by the Rev. W. Claxton, 



NO. 1464, VOL. 57] 



all of aberrant form ; and for Mr. J. Merrin a specimen ot 

 Aglais urticic with a silvery costal spot on the underside of the 

 forewings, a series of Melitaa aurinia, and an example of 

 Syrichthus malvie, ab. taras, taken near Gloucester. — Mr. 

 Kirkaldy exhibited a complete series of species of the genus 

 A/otonecta, L., specimens of the larva and imago of the very 

 rare Dtinostoma dilatalutn. Say., from Arizona, and specimens 

 of Antipalocoris iiiarshalli, Scott, from Ceylon, which was pre- 

 viously recorded from Corsica alone.— Papers were communi- 

 cated by the President on new or little-known species of African 

 butterflies, and by Mr. E. Meyrick on new Lepidoptera from 

 Australia and New Zealand. 



Cambridge. 

 Philosophical Society, November 8. — The following com- 

 munications were made : — On a method of demonstrating 

 assimilation in green plants, by Mr. F. Darwin, President. 

 Farmer has shown that the protoplasm ceases to circulate in an 

 Elodea leaf subjected to a stream of hydrogen and kept in the 

 dark ; also that if the preparation is illuminated the circulation 

 begins again. The cessation of the circulation depends on the 

 protoplasm being deprived of oxygen, the reappearance of the 

 movement is a consequence of the fresh supply of oxygen yield 

 by the chloroplasts in light. The experiment can be more 

 simply performed by mounting in water two or three Elodea 

 leaves under a single cover-glass, and sealing the preparation 

 with melted wax and paraffin. The leaves if kept in the dark 

 begin after a few hours to suffer for want of oxygen, and after 

 six or seven hours the protoplasm ceases to circulate. The 

 movement may be restored by exposing the preparations to sun- 

 light or to incandescent gas flame. Thus a demonstration, in 

 its way as interesting as Engelmann's bacterial method, may be 

 very simply performed. — Artificial culturesof.S'/^r«<w, a timber- 

 destroying fungus, by Prof. Marshall Ward. — On Encephalartos 

 ghellinckii, Lem., a rare Cycad, by Mr. A. C. Seward. The 

 author gave a short description of a plant of Encephalartos 

 gheHmckii, Lem., which had been obtained by Mr. Lynch, of 

 the Botanic Gardens, from Messrs. Saunders, of St. Albans. 

 This species differs in the form of the frond from the better-known 

 examples of the South African Cycadean genus Encephalartos, 

 and presents certain features which are of importance from a 

 palceobotanical point of view. 



Manchester. 

 Literary and Philosophical Society, November 2. — Mr. 

 J. Cosmo Melvill, President, in the chair. — Prof. Boyd Dawkins, 

 F.R.S., exhibited a sectiori of a spruce trunk which had been 

 completely hollowed out by a polysporous fungus. The resinous 

 pine-knots, however, are left entire, radiating from the centre. 

 He also pointed out that similar pine-knots (which he examined 

 in the museum at Basle) found in the interglacial deposit of 

 Darnten, and considered by Profs. Riitimeyer and Schwendauer 

 to be the remains of old basket-work or wattle-work, and to 

 prove the existence of interglacial man, are merely the result of 

 the nature decay of the wood, and are not artificial. He also 

 showed, under the microscope, a section of Fardel coal, showing 

 a resinous stem or knot from a carboniferous plant, the rest of 

 which has gone to form the black substance of the coal. Prof. 

 F. E. Weiss made some remarks on the exhibit, attributing the 

 destructive action to the fungus Trametes pint, and explained 

 how the fungus attacked the centre of the tree, making its way 

 in through the decayed core of broken branches. — Prof. Weiss 

 then exhibited a specimen of Plowrightia morbosa, the black- 

 knot, on a branch of cherry collected in Canada, where it has 

 been the cause of considerable destruction of cherry-trees. He 

 also exhibited the fructifications of Peziza artiginosa, the green- 

 rot of the oak. The fructifications of this fungus, which are 

 rarely met with, were collected at New Abbey, near Dumfries. 

 A discussion followed, which also turned on the subject of the 

 colouring-matter of fungi. — Prof. H. B. Dixon, F.R.S., ex- 

 hibited and remarked upon a number of lantern photographs of 

 explosion- flames. 



Paris. 

 Academy of Sciences, November 8. — M. A. Chatin in the 

 chair. — On the influence of hygroscopic substances upon the 

 combination of hydrogen and oxygen, by M. Berthelot. The 

 hygroscopic substances chosen were hydrogen chloride, boron 

 fluoride, and sulphurous anhydride as giving homogeneous 

 systems for liquids, concentrated sulphuric acid ; for solids, phos- 

 phorus pentoxide, baryta, quick -lime, and potassium hydroxide. 

 Of these the three gases w^re found to be without appreciable 

 effect in accelerating the reaction ; with sulphuric acid, the 



