1 84 



NA TURE 



[June 13, 1878 



complete deductions from the measui-es of sun-spots and facultc 

 in that year, if they can be prepared for press in time, 

 leaving the complete results for the years 1873 to 1875 to be 

 included in the next volume ; the areas, as distinct from posi- 

 tions, having been already printed in the volumes for 1874 and 

 1875. 



The usual magnetical and meteorological observations have 

 been carried on, and considerable progress made with their 

 reduction. 



The following are the principal results for magnetic elements 

 in the year 1877 : — 



Approximate mean westerly declination 18° 57'. 



Mean horizontal force . . j 3-90i (in English units). 



( 1799 (m metric units). 



o / // 



167 38 46 (by 9-inch needles). 

 67 39 54 (by 6-inch needles). 

 67 40 40 (by 3-inch needles). 



Under the head of Extraneous Work, information is given as 

 to the reduction of the Transit of Venus observations. 



At the date of the last Report the determination of the 

 longitudes of the British stations was not quite complete (that of 

 Kerguelen being then imperfect). But, under a demand from 

 the House of Commons, a strong effort was made to finish all 

 introductory calculations, and to effect computations of solar 

 parallax by comparing all eye-observations of ingress of Venus 

 among themselves, and all eye-observations of egress of Venus 

 among themselves. The different stages of phenomena at the 

 ingress were discriminated by Capt. Tupman with great care, 

 and Sir George Airy believes with great general success, although 

 Capt. Tupman himself has been induced lately to modify his 

 interpretation of the observers' language in one or two instances. 

 Finally, a report was made to the Government on July 5, giving 

 as the mean result for mean solar parallax 8"76, the results from 

 ingress and from egress, however, differing to the extent of 

 o"*ii. A more, complete calculation by the Astronomer-Royal, 

 including in one series the observations both at ingress an ! at 

 egress, and recognising the possible errors of R.A. and N.P.D., 

 gave sensibly the same mean result for parallax. This is 

 liable to no error except from the interpretation of observers' 

 language. All has subsequently been re-examined by Capt. 

 Tupman ; different interpretations have, in a few instances, been 

 put on the records ; several observations from colonial stations 

 have been combined ; instead of using different phases in the 

 observations (both of ingress and of egress), attempts have been 

 made to ascertain the one phase of ' ' contact of limbs ; " the notes 

 of a few unpractised observers have been rejected, and the result 

 for parallax has been increased to 8"'82 or 8"'83. 



The numerous photographs taken at the various stations 

 had been carefully measured by Mr. Burton, and have since been 

 re-measured by Capt. Tupman ; and (by photographs of Mr. 

 De la Rue's scale of equal parts) the measure of photographic 

 distortion had been well ascertained. But the results from pho- 

 tography have disappointed Sir George Airy much. The failure 

 has arisen perhaps sometimes from irregularity of limb, or from 

 atmospheric distortion, but more frequently from faintness and 

 from want of clear definition. Many photographs which to the 

 eye appeared good, lost all strength and sharpness when placed 

 under the measuring microscope. It was once remarked to Sir 

 George Airy, '« You might as well try to measure the zodiacal 

 light. A final result, 8"- 17, the report states, was obtained from 

 Mr. Burton s measures, and 8"'o8 from Capt. Tupman's. 



The Report next alludes to the progress made in the numerical 

 lunar theory. The developments of the effect of every pos- 

 sible error (expressed as a symbolical variation) in the co-efficients 

 and arguments of the assumed lunar ordinates upon every term 

 in the three fundamental expansions of— (i) Areas in the eclip- 

 tic, (2) Radial forces in the ecliptic, (3) Forces normal to the 

 ecliptic — have been computed and printed. The corresponding 

 solar perturbing forces have been computed entirely for the first of 

 these (care being taken to extend the decimal calculation further 

 for those terms whose effect may probably be increased in solution 

 of the equations, a process in which many figures are almost neces- 

 sarily wasted), and partially forthe secondand third. Until all have 

 been completed the Astronomer-Royal cannot draw any positive 

 inference from the comparison of these terms with those of the 

 ordinate expansions ; but a cursory collation of those' relating to 

 me areas led him to suppose that there might be some error in 

 tne computations of the annual equation and related terms. A 



most jealous re-examination has, however, detected nothing, and 

 has confirmed Sir George Airy's belief in the general accuracy of 

 the numerical computations. 



Finally, Sir George Airy strongly vu-ges upon the Board the 

 necessity for the erection of a separate room for the library of 

 the Observatory. 



COSMICAL RESULTS OF THE MODERN 

 HEAT THEORY 



TN the Sitzungsherichte der Wiener Akadtmieder Wissenschaf/en, 

 Herr J. Loschmidt has published a treatise on the equi- 

 librium of temperature in a system of heavenly bodies with regard 

 to gravitation, from which we note the following highly interest- 

 ing details : — " Sir W. Thomson and Clausius simultaneously,^ 

 drew from their researches the surprising conclusion that the 

 whole universe at some definite period, however remote, would 

 infallibly come to an end. First, all ponderous masses in the 

 universe will eventually have united to one enormous heavenly 

 body ; and secondly, upon this body all visible motion will have 

 ceased, all forces having changed to mere molecular motion, 

 which in the shape of heat of universally uniform temperature will 

 be spread in this mass. This state of general death will then last 

 eternally." Herr Loschmidt, in the course of his researches, has 

 arrived at widely different conclusions. He begins by adopting 

 the general view that the sun is in a state of slow progression of 

 cooling, and that the time will unavoidably arrive when his sur- 

 face will have solidified, long after all his planets have fallen 

 in upon him, and after ^his upper and partly also his lower 

 strata have assumed very nearly the temperature of the surround- 

 ing universal space. But granting that thus a period of rest and 

 death will have arrived for our solar system, Herr Loschmidt 

 maintains, at the same time, that this period cannot be of 

 unlimited duration ; the state of things just described can, 

 according to his views, not be a state of equilibrium. *' The 

 previous liquid state of the sun has caused a continued mixture 

 of the warmer parts near the centre with the colder ones near the 

 surface. Thus, however, the equilibrium of temperature, which 

 requires a certain increase of temperature towards the interior, 

 was rendered impossible. At the moment of solidification of the 

 external layers the deeper ones will be far colder than the theory 

 of the state of equilibrium demands. Because, according to this 

 theory, the surface should have the temperature of universal 

 space (about — 140° C. according to Pouillet), but this tempera- 

 ture should rapidly increase towards the interior, reaching at the 

 centre the enormous figure of 250,0x30,000° C. And it is just 

 because at the moment of the beginning of solidification of the 

 sun no such distribution of temperature took place in the interior, 

 that the state above referred to cannot be of eternal duration. 

 During an extremely long period, in spite of the low temperature 

 of his surface, the solidifying sun will constantly absorb radiant 

 heat from the store in the universe and will concentrate this heat 

 in his interior. We suppose, for a moment, that it would be 

 physically possible that this process of absorption is carried on 

 to the end without the inclosed and dissociated gases in the 

 interior breaking through the solidified surface or crust on account 

 of their enormous tension. We then calculate the amount of heat 

 accumulated in the end and find that it would easily suffice to raise 

 the entire solar mass to |ths of that temperature which the state 

 of equilibrium demands at the centre, viz,, to 100,000,000^ C. 

 This figure is raised if the average molecule of the solar mass, 

 instead of being supposed to be oi the density of oxygen, is taken 

 to be of the density of carbonate of lime ; in that case it would 

 be 125,000,000° C. We may compare these results to the quan- 

 tity of heat which was.produced during the condensation of the 

 solar system from the cosmical nebula, according to the theory 

 of Laplace and Kant. Helmholtz has calculated that the heat 

 thus generated would suffice, to raise the solar mass to a tem- 

 perature of 28,611,000° C, if it is supposed to have the heat 

 capacity of water. If, instead of water, other substances are 

 taken as starting points, this temperature is considerably raised ; 

 so in the case of carbonate of lime or silicic acid, the heat 

 capacity of which is 0'2, the resulting temperature would be 

 140,000,000° C. 



" The close correspondence of both amounts speaks in favour 

 of a periodicity in the history 0/ solar systems. In the first por- 

 tion of its cosmical period the dark solidified body absorbs heat 



^ [Clausius verified Thomson's statements about dissipation just as he 

 verified (after experiment had proved it) J. Thomson's statement of the 

 loweriEg of the freezing-point of water by pressure. Some Germans still 

 call this " simultaneous discovery." Helmholtz, at least, does not.^Eo.] 



