l8o 



NA TURE 



[Fekkuary i6, 1905 



two to eight weeks after the paraplegia was complete, living 

 altogether up to eleven or twelve months. At no time were 

 any Trvpanosomata found in the blood, nor /)oi( mortem 

 in the viscera, or glands. But in the spinal cord they were 

 present in small numbers, and inoculation of the cord 

 into other rats has produced similar symptoms, whilst in- 

 oculation of the organs has been negative. In sections of 

 the spinal cord amoeboid and adult forms of the Trypano- 

 soma have been found, and also those lesions which Dr. 

 .\Iott found in the nervous system of man in cases of 

 sleeping sickness, viz., a considerable cellular exudation 

 around the vessels. This is not found in monkeys, in which 

 the organisms become generalised, and do not get localised 

 in the nervous system as is the case in rats. 



These experiments go to show that the organisms asso- 

 ciated with the diseases of Gambia fever and sleeping 

 .sickness, which are thought by some to be the same disease 

 in different stages, are quite distinct in their effects, and 

 they are also distinct morphologically ; that the Trypano- 

 soma of sleeping sickness can be inoculated into rats, which 

 has been denied ; and that there is a great similarity in 

 the lesions produced in the nervous systems of man and of 

 rats, and in the localisation of the disease to the nervous 

 system. 



From experiments made, a double infection would seem 

 to be quite possible, and to be a likely event in these 

 diseases. 



January 26. — "' On the .Modulus of Torsional Rigidity oi 

 Quartz Fibres and its Temperature Coefficient. " By Dr. Frank 

 Horton, St. John's College, Cambridge, late Mackinnon 

 .Student. Communicated by Prof. J. J. Thomson, F'.R.S. 



In this research the dynamical method of experimenting 

 was employed, and the investigaton was divided into three 

 parts : — 



(i) The determination of the absolute value of the torsion 

 modulus. 



(2) The variation of the modulus between 15° C. and 

 100° C. 



(3) The variation of the modulus between 20° C. and 

 1000° C. 



The radii of the fibres used were determined by measur- 

 ing their circumferences, the fibres being rolled between 

 two line glass capillary tubes and the number of revolutions 

 made in travelling a distance of 5 mm. counted. By this 

 method fibres of diameter o.ooi cm. were measured to 

 0.0 1 per cent. 



In the second part of the research the jacket enclosing 

 the fibre was heated by using the vapours of various liquids 

 boiling under atmospheric pressure. The modulus of 

 rigidity was found to increase as a linear function of the 

 temperature, but the values of the temperature coefficient 

 of the modulus obtained from different fibres were con- 

 siderably different. In the experiments between 20° C. and 

 1000° C. the fibres were suspended inside a platinum tube, 

 which was heated electrically. It was found that the 

 modulus of rigidity increased with the temperature, at 

 first as a linear function of it, but as the temperature rose 

 the rate of increase gradually diminished and a maximum 

 rigidity was attained at about 880° C. .'\fter passing this 

 point the rigidity decreased very rapidlv with increase of 

 temperature. 



" Note on the Cause of the Period of Chemical Induction 

 in the L'nion of Hydrogen and Chlorine." By D. L. 

 Chapman and C. H, Burgess. Communicated bv Prof. 

 II. B. Dixon. 



The induction period in the union of hydrogen and 

 chlorine exposed to light, which has been ascribed by 

 various authors either to a change in the physical con- 

 dition of the chlorine or of the mixture of hydrogen and 

 chlorine, or to the primary formation of an unstable inter- 

 mediate compound, has been shown by the authors to be 

 due to impurities. The impurities are those which react 

 with chlorine, such as ammonia and sulphur dioxide. At 

 the ordinary temperature in the dark the reaction between 

 these substances and chlorine is not completed. In the 

 light or by raising the tempernlure these impurities can 

 be entirely removed by the chlorine. The time required 

 for their removal is the induction period during which 

 NO. 1842, VOL. 71] 



the chlorine is rendered incapable of combining with the 

 hydrogen. 



It has been hitherto supposed that an induced mi.xture 

 of hydrogen and chlorine if left to stand for some time in the 

 dark must be again induced before combination will proceed 

 at its normal rate. This is not ihe case if a quartz actino- 

 meter is substituted for a glass one. 



" The Theory of Synnnetrical Optical Objectives. — Pan 

 II." Bv S. D. Chalmers. Communicated bv Prof. Larmur, 

 Sec.R..S. 



In photographic objectives, consisting of two similar 

 lenses symmetrical to a central stop, the back member is 

 generally corrected for spherical and chromatic aberra- 

 tions, astigmatism, and curvature of field for distant 

 objects, and thus the whole system is perfectly corrected 

 for unit magnification. The present paper discusses the 

 aberrations for distant objects. In part i. it was proved 

 that, to the first appro.ximation, the above defects are 

 corrected in the whole system when they are corrected in 

 the single member. By geometrical constructions, using 

 the symmetry with respect to the axis and to the stop, 

 these results are extended to practical systems. The paths 

 of parallel rays, incident on the combined system, are 

 obtained from those of two sets of parallel rays incident 

 on the single system ; the aberrations of the combined 

 system are expressed in terms of the single system with 

 small errors — negligible in practical systems — due to the 

 image of the stop being imperfecft. 



" Exterior Ballistics. Error of the Day and other 

 Corrections to Naval Range Tables." Bv Prof. Geo. 

 Forbes, F.R.S. 



Gun-sights are always marked for standard conditions 

 of muzzle velocity (m.v.) and air density (a.d.). When 

 cither of these change the sights must be corrected. The 

 author finds from theorv that if a.d. is increased tn fold, 

 and the range is diminished m fold, then the elevation 

 and time-of-flight must be diminished 111 fold ; and, em- 

 pirically, that up to 10° of elevation (10,000 yards for a 

 12" gun) elevation varies very closely as i [m.v.]", as iti 

 vacuo. On these laws he calculated from the naval 

 range table of a 12" gun, 85olbs. shot, 2463 m.v., at 2, 

 4, 6, 8, and 10 thousand yards, the table for a 6" gun, 

 loolb. shot, 1960ft. sees. The elevations only differed 

 from the Naval 6" table by — i, —4, —2, -I- 2, and +4 

 min. of arc. 



The laws, therefore, may be applied with perfect con- 

 fidence for the comparati\elv small \'ariations that occur 

 in any one gun. 



Linnean Society, [anuaiy 19. — Prof. \V. A. Ilerdman, 

 F.R.S., president, in" the chair.— The Rev T. R. R. 

 Stebbing: exhibited and explained specimens of Crustacea, 

 in various ways remarkable for structure, habits, habitat, 

 or colouring. — Botanical collecting : Dr. A. Henry. The 

 actual methods were briefly alluded to, stress being laid on 

 truthful labelling of the specimens at the moment of col- 

 lection, instead of months afterwards, when identical 

 numbers were often given to plants of different provenance'. 

 Dr. Henry described observations made by him in China. 

 He alluded to mimicry in plants, in the case of two species 

 of Lysimachia (a protomorphic genus in China), one of 

 which mimicked Paris quadrijolia, with 4 leaves, while the 

 other recalled another species of Paris with 10-12 leaves. 

 He referred also to the extraordinary richness of species 

 on calcareous soils as compared with other soils, a fact 

 constantly seen in China, and well marked also in France, 

 and asked for some explanation. In China, as elsewhere, 

 pure woods were rare, being only formed by a few 

 conifers, like .ihies Fars^esii at high altitudes in Hupch. 

 Cuprcsstis funebris in the same province at lower levels 

 (the home of the Reeves's pheasant), I'iniis Massoniana 

 (almost everywhere in the central and southern provinces), 

 other species of Pinus more local ; also certain species of 

 oak widely distributed; and .Mntis iiepalensis in Yunnan. 

 1 lie explanation of the occurrence of pure forests was also 

 a subject not completely understood : e.g. in this countrv 

 ash seeded freely, and in some places for a time looked as 

 if it would grow inl(. a pure wood: but apparentlv pure 



