574 



NATURE 



[April II, 1889 



movable coil, sliding in guides so as to vary the constant in known 

 proportions. Two controlling magnets are carried on opposite 

 sides of a sleeve sliding on a central tube, inclosing the long 

 fibre, and a small hollow copper cylinder in oil acts as damper. 

 The tangent law was found by calculation to be practically 

 correct up to 15^, and the scale is curved so as to read tan- 

 gents on a scale of equal divisions. To give this result 

 the approximate polar equation to the curve is shown to be 

 r — f{i + 0'207fl"^ + o'oaege-*). In standardizing the instru- 

 ment a known current is sent through it from the Clark cell, 

 and the controlling magnets adjusted till the spot comes to a 

 fiducial mark on the scale. By varying the position of the coil, 

 currents ranging from O'coi to 0'4 ampere, can be measured. 

 — On the measurement of high specific resistances, by Prof. 

 Thrclfall. The chief points dealt with are, the means for pro- 

 ducing thin plates of material of known dimensions, the form 

 and methods of magnetizing the needles, and the arrangement 

 of suspension found necessary when great sensibility is required. 

 For producing the plates, two plane platinized brass slabs are 

 used, and kept at a known distance apart by micrometer screws, 

 whilst the material is melted between them. The screws are 

 then withdrawn, and the resistance determined by comparison 

 with a megohm, using different E.M.F.'s in the two cases so as 

 to obtain about equal deflections. As regards the galvanometer, 

 after many unsatisfactory attempts to use one made according to 

 the Messrs. Gray's pattern, the coils of that instrument were 

 mounted in the ordinary way, and used with an astatic com- 

 bination of magnetized steel disks. Extreme care was taken to 

 obtain disks exactly similar, and a pair of electro-magnets were 

 made to magnetize ihem in situ, so as to obtain great astaticism. 

 For suspending the magnets, quartz fibres were found greatly 

 superior to silk, the zero of the instrument being very indefinite, 

 even with a silk fibre 30 inches long. Considerable difficulty 

 was experienced in attaching the mirror to the needle on account 

 of the distortion produced by ordinary cements ; slow drying 

 white paint was ultimately used and found satisfactory. — On the 

 measurement of the resistance of imperfectly purified sulphur, by 

 Prof. Threlfall and Mr. A. Pollock. The apparatus used is 

 described in the previous paper, the galvanometer of 16,000 

 thms being arranged to give one division for 2 x lo"-'- amperes. 

 A mean of the results obtained gives about 11 x 10'^ ohms per 

 cubic centimetre as the specific resistance. In performing the 

 experiments many precautions were required to prevent air cur- 

 rents and magnetic disturbances, and paraffin keys were found to 

 give much better insulation than ebonite ones. In conclusion, the 

 authors enumerate the chief points to which attention should be 

 paid in designing and using very sensitive galvanometers. They 

 consider it desirable to use quartz fibres at least 6 feet long, to 

 provide very fine adjustment for the controlling magnets, whose 

 supports should be independent of the suspension arrangement, 

 and believe that the whole should be placed in a thick soft iron 

 cylinder. Mr. Boys, speaking of attaching mirrors to wires, said he 

 found a very small speck of shellac varnish to be very satisfactory. 

 As regards quartz fibres. Prof. Threlfall's method of producing 

 them differed materially from his, and the fibres were much 

 thicker. He considered it quite unnecessary to use fibres any- 

 thing like 6 feet long, and thought 15 inches quite sufficient 

 where the weight to be supported was not large. Prof. Ayrton 

 regarded the results obtained from Clark's cells to be of extreme 

 scientific and commercial • importance, for they showed that a 

 very convenient standard of E.M.F. could also be used as a 

 standard for current. Prof. Thompson, after commenting on 

 the convenience of good E.M.F. standards, expressed a hope 

 that Prof. Threlfall would be able to suggest a convenient method 

 for producing a standard ampere. 



Royal Meteorological Society, March 20. — Dr. W. Marcet, 

 F.R.S., President, in the chair. — Dr. Marcet delivered an ad- 

 dress on " The Sun : its Heat and Light," in which he said that 

 the source or origin of all meteorological phenomena is the sun, 

 which sends or radiates its heat to the earth through the mole- 

 cular vibration of the invisible matter connecting earth with 

 space. If there were no air and moisture we should feel the 

 sun's heat to a much greater extent. After the sun's rays have 

 reached the earth, a portion of the heat they bring with them is 

 absorbed by the earth and terrestrial objects, another is converted 

 into motion, and a third is reflected into space. After describ- 

 ing the various actinometers and other instruments used for de- 

 termining the amount of solar radiation. Dr. Marcet showed that 

 the temperature of the solar rays falls rapidly when tested at in- 

 creasing altitudes in a balloon. He then gave an account of 



some observations made by Mr. Glaisher in the celebrated 

 balloon ascent which he and Mr. Coxwell made at Wolver- 

 hampton on September 5, 1862, when they reached a height of 

 about seven miles above the earth's surface. Regarding the 

 transformation of solar heat into motion, a very interesting 

 illustration is afforded by the radiometer, in which the direct in- 

 fluence of the sun's rays causes a light vane to rotate ; while 

 another illustration of the mechanical effects of heat upon fluids 

 is their conversion into what is known as the spheroidal con- 

 dition. In connection with this Dr. Marcet explained how by 

 wetting his hand he could pass it through molten lead without 

 injury. He also related the case of Henry Hall, one of the 

 keepers of the Eddystone Lighthouse, who, on the occasi n of 

 the fire which destroyed the lighthouse on December 4, 1755, 

 accidentally swallowed some molten lead, but did not die till 

 several days afterwards, when a piece of lead was taken out of 

 his stomach. Dr. Marcet then briefly drew attention to the 

 sun's light, stating that the passage of the sun's light through 

 our atmosphere alters it in kind to a great and remarkable ex- 

 tent. Light can be decomposed into its elementary colours. In 

 connection with this branch of the subject Dr. Marcet per- 

 formed a number of experiments, including, among others, that 

 of passing a ray of light through a glass freed from dust, when 

 the ray disappears within the vessel, but reappears on the other 

 side, showing that the power to form light was there, though 

 not the material for this power to act upon. Dr. Marcet con- 

 cluded his very interesting address by describing the various 

 forms of sunshine recorders. — The meeting was then adjourned 

 in order to afford the Fellows and their friends an opportunity 

 of inspecting the Exhibition of Instruments opened on the 

 previous evening. x\ full account of this Exhibition has already 

 been given on p. 523. 



Geological Society, March 20.— W. T. Blanford, F.R.S., 

 President, in the chair. — The following communications were 

 read : — Supplementary note to a paper on the rocks of the At- 

 lantic coast of Canada, by Sir J. W. Dawson, F. R.S. — The 

 occurrence of colloid silica in the Lower Chalk of Berkshire 

 and Wiltshire, by Mr. W. Hill and Mr. A. J. Jukes-Browne. — 

 Note on the pelvis of Ornithopsis, by Prof. H. G. Seeley, 

 F.R.S. The remains preserved in Mr. Leed's collection at 

 Eyebury, and described by Mr. Hulke, are the largest and most 

 perfect pelvic bones of a Saurischian known in this country. 

 An examination showed that the bones of the right and left 

 sides were united in the median line almost throughout their 

 length by a median suture, and that they formed a saddle-shaped 

 surface internally from front to back. After giving a detailed 

 description of the pubis and ischium, the author stated that he 

 was not aware that this type of pelvis had been previously ob- 

 served. He noted that the antero-posterior concavity between 

 the anterior symphysis of the pubic bones and the posterior 

 symphysis of the ischia was a well-marked characteristic of 

 Saurischian reptiles, but that it remained to be determined to 

 what extent the median union of the pubic bones was developed 

 in the group. It was impossible to judge of the form of the 

 ilium from the imperfect fragment preserved, but it did not make 

 any recognizable approximation to the bone in those American 

 genera which offered the closest resemblance of form to the pubis 

 and ischium. There were several minor differences of propor- 

 tion between the bones from the Oxford Clay and those from the 

 Wealden of the Isle of Wight, and the former differed in ways 

 pointed out from iMorosaurus, Diplodociis, and Brontosaiirus, 

 though there were resemblances. 



Zoological Society, March 19. — Prof. Flower, F. R.S., 

 President, in the chair. — The Secretary read a list of the fishes 

 collected at Constantinople and sent to the Society by Dr. E. D. 

 Dickson. The species were sixty-six in number, and had been 

 determined by Mr. G. A. Boulenger. — Mr. Tegetmeier exhibited 

 a female Gold Pheasant in male plumage, and a curiously distorted 

 pair of horns of the Ibex of Cashmir. — The Rev. A. H. Cooke 

 read a paper on the position of the land shells of Australia and 

 the adjacent islands, commonly referred to the genus Pliysa, which 

 it was shown (mainly from an examination of the radula) were 

 really more nearly allied to the genus LimucBa. Mr. Cooke pro- 

 posed to refer these species to the genus Bulinus, established by 

 Adansonin 1757. — Mr. G. A. Boulenger read notes on some spe- 

 cimens of Lizards belonging to the Zoological Museum of Hale, 

 which had been sent to him for examination. To these notes were 

 appended revised descriptions of two Lizards from the Argentine 

 Republic, Gymnodactyhis horridiis and Uroitrophus scapula- 

 tus.—K communication was read from Prof. W. N. Parker, 



