October 1 1, 1894J 



NA TURE 



hl^ 



The Newtonian Constant of Gravitation. 



I SHOULD be obliged if you would allow me to make a 

 correction in my lecture at the Royal Institution, published in 

 Nature, Aug. 2, 9. and 23, on page 331. I have stated that 

 in pieces of apparatus geometrically similar but of different 

 dimensions, the disturbances due to uncertain convection currents 

 .ire likely to be in the proportion of the seventh power of the 

 linear dimensions. Having discussed this at some length lately 

 with Prof. Poynting, I find that I was in error, and that in reality 

 the disturbances would be proportional to the fifth power of the 

 linear dimensions if the circulation of the air were so extremely 

 slow as to be ste.idy. If, however, its velocity were sufficient to 

 give rise to unsteadiness, the rate at which momentum would be 

 given to the suspended portion of the apparatus would depend 

 on the square of the velocity, at least in pari, and .-is the part 

 depending on the square increased in importance the disturbance 

 would gradually rise to the eighth power. So long, therefore, 

 as the apparatus is small enough to prevent terms involving the 

 square of the velocity from being appreciable, the ratio of the 

 disturbance to the couple to be measured or the stability is 

 the same whatever the size ; but as soon as the apparatus 

 exceeds this, then the disadvantage of size very rapidly becomes 

 evident. 



Of course the objection due to the great increase of time 

 which must elapse between the handling of apparatus and its 

 being fit for observations to be made, which accompanies 

 increase of size, remains. 



As the consideration of the relation between disturbance and 

 couple to be measured, and its variation with linear dimensions, 

 is a matter of great importance in the design of most instru- 

 ments in which the movements of a suspended system supply 

 the means of measurement, there is an additional reason for 

 correcting in these columns the error that I made. 



C. V. Boys. 



On Some Temperature-Variations in France and 

 Greenland. 



The relations indicated in the iiagram sent herewith are, I 

 think, instructive ; and they might perhaps be found to contain 

 some useful clues to coming weather. 



This diagram has two kinds of curves, dotted line, and con- 

 tinuous. Both are smoothed curves. In the former, the actual 



1005 '10 '15 '20 '25 '30 'S5 '40 "45 'SO "55 '60 83 '70 "75 '80 'OS '90 '9S 



values have been smoothed with averages of five ; and in the 

 latter, those averages have, in their turn, been treated in the 

 same way. High points in all the curves denote heat ; low 

 points cold. 



The first pair of curves (a) show, by averages, the variation 

 in th; number of frost days in Paris in October to April of each 

 cold season since i8c6. (I designate each cold season by the 



NO. I ^0 2, VOL. 



5o] 



year in which it tnds ; 1806 meaning 1S05 6, &c.). These are 

 inverted curves, the numbers increasing downwards. They 

 present a succession of (say) five obvious waves, which, with 

 regard to the crest intervals, are neither wholly regular nor 

 wholly irregular, the intervals of the smoother curv-e being, in 

 series, 12, 15, iS, and 17 years. 



The second pair of curves (b) show the variation in mean 

 temperature of July at Paris during the same period ; and we 

 may perceive in these a general correspondence to the first 

 curves, with, however, a distinct tendency to lag somewhat. 



There is a good deal of general similarity, of course, between 

 the weather of Paris and our own, and between the longer waves 

 of variation of July and those of the whole summer. Hence we 

 find, e.g., that a once smoothed curve of mean temperature of 

 summer at Greenwich presents obvious minima in the years 

 1814, 1S39, 1S62, and 1881. Compare this with the Paris July 

 curve. 



It is known that in our climate a severe winter tends to be 

 followed by a cool summer ; but the facts here presented are, it 

 will be perceived, of a somewhat different order, and wider 

 scope. 



The third pair of curves (c) relate to Jakobshavn, on the 

 west coast of Greenland, and show the smoothed variations in 

 mean temperature of winter (December-February) for a series 

 of years. These curves are short comp.ired with the others, and 

 are interrupted at one part ; but so far as they go, they seem 

 to present a similar variation, with further lag ; so that, as com- 

 pared with the Paris frost curve, we find the phases have come 

 to be nearly opposite. Our European winters, indeed, seem to 

 be generally opposite to those of Greenland. This is pointed 

 out, as regards Vienna, by Dr. Hann in the paper from which 

 those Jakobshavn figures are obtained. {.Met. Zeits. 1890, p. 

 II3-) 



By way of comparing these curves, it may be useful to note 

 the lowest points of the three once-smoothed curves ; and the 

 intervals between those of the same curve and of dill'erent 

 curves. (The intervals, in years, are given in brackets.) 



Paris, frost, 1814(25), 1839(17), 1856(22), 1878(H), 1889 



(I) (3) (6) (3) 



Paris, July, 1S15 (27), 1842 (20), 1862 (19) iSSi (9), 1S90 



(2) (3) (3) 



Jakobshavn, winter, 1S44 (21)1 1865 (19), 1S84. 



The fact of this lagging correspondence would appear to 

 suggest that the general variations of our winter seasons are, in 

 some measure, a key to those of approaching summers, and also, 

 if the Jakobshavn correspondence were confirmed by a longer 

 series of data, to those of approaching winters in Greenland. 



An explanation of these curious facts may perhaps be supplied 

 by those who have a comprehensive knowledge of polar meteor- 

 ology and its relations. A. B. M. 



New Element in the Sulphur Group. 



Dr. B. Brauner, of Prag, in iSSS made a careful investiga- 

 tion of the atomic weight of tellurium, an account of which 

 will be found in C. S.J. 320, p. 382. In accordance with 

 Messrs. Newland's and MendeleeCs Periodic Law, tellurium 

 should have, if pure, an atomic weight of 125, or even lower. 



Prof. D. Mendelcef takes Sb = 122, Te = 125, I = 127. 

 Taking the latest numbers for antimony and iodine (Sb = 120, 

 I = 126 8), Dr. Brauner proceeds to investigate the atomic 

 weight of Te, for which he finds by a great number of 

 experiments the number I27'65. As is only to be expected 

 from such a staunch advocate of the Periodic Law, he at once 

 came to the conclusion that neither himself nor former experi- 

 menters (Berzelius, in 1S12, 1S18 and 1S32 ; von Hauer, in 

 1857, &c.) had been dealing with the pure clement. As he 

 puts it, tellurium is not an element. 



Tellurium prepared from the dibromide gave the high atomic 

 weight of 130. Prepared from the tetrabromide, which Latter 

 was distilled in vacuo, the resulting element being distilled in a 

 current of hydrogen, Te = i27'65. Under these circumstances, 

 he says, no doubt one constituent of "tellurium" partly 

 escapes, thus reducing the atomic weight. He terms tellurium 

 the g.adolinium of the sulphur group. 



In the followirg year, 18S9, Prof. Mendelcef predicted 

 (Faraday Lecture, C. S. J. 323, p. 649) an element with 

 atomic weight 212, which he calls Dvi -( = Bi - ) tellurium, for 

 which he suggests the symbol Dt, and predicts the following 



