May 17, 1883] 



NA TURE 



7i 



The Rendiconti of the Reale Istituto Lombardo di Science 



Lettcre for February and March, 1S83, contains papers by G. 

 Ascoli, en Irish glosses, especially those of the Atnbrosian 

 Codex ; by M. E. E. Beltrami, on the theiry of magnetic layers ; 

 by Z. Vol'a, on an unpublished drama of Luigi Ceretti ; by G. 

 A. Maggi, on the transmission of undulatory motion, and espe- 

 cially of luminous waves, from o e isotropic medium to'another ; 

 by P. F. Denza, on the observations of the transit of Venus 

 made at the observatory of the Collegio Carlo Alberto in 

 Moncalieri. 



SOCIETIES AND ACADEMIES 

 London 



Royal Society, April 12. — "The principal cause of the large 

 errors at present existing between the positions of the Moon, de- 

 duced from Hansen's Tables and observation ; and the cause of 

 an apparent increase in the secular acceleration in the Moon's 

 mean motion required by Hansen's Tables, or of an apparent 

 change i 1 the time of the Earth's rotation," by E.J. Stone, F. K.S. 



The errors in the lunar theory have been traced t > the effects of 

 changes in the unit of lime which have, apparently unconsciously, 

 been introduced, from time to time, into astronomy with changes 

 in the adopted data. 



The argument is clearly seen by a consideration of the different 

 expressions for the longitudes of, what may be called, the mean 

 sun which have been ad opted for the determination of the sidereal 

 times at mean noon. 



\{ B, //, and V denote the longitudes of the mean sun accord- 

 ing to Bessel, Hansen, and Le Verrier, we have for 1850, 

 January I, Paris mean noon, + / 



B = 2So 46 36-12 + T2o,6o27-6iSiS4<+o-oooi22i8o5 . t- 

 //=2So46 43-20 +1296027-674055/ + 0-0001106850 . I- 

 K=28o 46 43-51 + I2q5o27-67S4DO/ + o-oooiio7}oo . f". 



Ir. all these expressions the unit of time has been supposed to 

 be a Julian year 1 if 365-25 ruein solar days. The constant 1 

 ences 7"'oS and 7' '39 in B-H and B-Vvxe. not unimportant, for 

 they introduce abrupt changes in the record of time ; hut the 

 differences in the coefficients of / and /- show that the same unit 

 of time can ..t have l.een adopted in these expressions. The 

 measure of time must be continuous ; let, therefore, 1 and (r +.\) 

 be the units in B and H, 



then 1296027-618184. /+O'cooi22i8o5/ 2 



= 1296027-674055/(1+*) + 0-0001106850 / 2 (i+.r) 2 . 



If, therefore, »= 1296027-674055 



r _ _ o'o5587i , 0-000114955./ 



To reconcile B and H, therefore, x must contain a variable term. 

 Similar remarks apply to the difference between B and V. 



Now let ./Vbe the moon's mean motion referred to I as the 

 unit of time, and (N+ SA 7 ) the moon's mean motion referred to 

 (l+x) as the unit of time, 



then (N+SN) (i+x) = N, 



and tSN = J 0-055871 . /- 0-0000114955 . /= j 



= o-747./-i"-S4(-4) 2 . 



But Hansen determined his mean motion of the moon so as to 

 force an agreement between his theory and observations reduced 

 with Bes-el's unit 1 ; and his tables, therefore, represented the 

 observation 5 well formany years, whilst I was adopted as the 

 unit of time ; but directly the unit of time was changed by the 

 adoption either of H or V, then the effects of the erroneous 

 determination of the moon's mean motion by Hansen became 

 apparent. The change of error in longitude of Hansen's Lunar 

 Tables between 1864, when Le Verrier's Solar Tables were 

 adopted in the Nautical Almanac, and 1880, amounts to more 

 than 10". 



The effect of the change of unit is also shown in the com- 

 parison of Le Verrier's Solar Tables with observation, but of 

 course only to about the thirteenth part of the amount shown by 

 the Lunar Tables. The necessity of adopting some definite unit 

 of time by fixing the constants in the expression for the longitude 

 of the mean sun is insisted upon.^ 



If Z + « / + S fi is the expression adopted for the longitude 

 of the mean sun, the quantities Z,„ «„, S , must never be 

 changed. The correction SI, which from time to time may 

 appear necessary to obtain the mean longitude of the sun from 

 the longitude of the mean sun must not be allowed to change 

 the adopted values of Z (l , ;;„, and S , The true longitude of the 

 sun will then 



— Z + »„/ + S t- + SL + periodic terms. 

 It would appear that speculations respecting changes in the time 

 of rotation of the earth on its axis are at lea-t premature until 

 the theories have been revised with a unit of time freed from 

 changes of adopted constants which are at present inextricably 

 mixed up with any effects which would result from a change in 

 the time of rotation of the earth on its axi ;. 



The longitude of the mean sun when properly investigited, 

 differs from the mem longitude of the sun by a secular term — 



0-3113 



V 100 / 



As this difference has been usually neglected in the determination 

 of the sidereal time at mean moon, an error of about 



13x0-3113. (4)"' 01 " 4 "(Too)" 



has been thrown upon this secular acceleration of the moon'-, 

 mean motion. This accounts for the difference between Adam's 

 theoretical value, and that deduced from eclipse observation!;. 



Chemical Society, May 3.— Dr. W. H. Perkin, president, 

 in the chair. — The following papers were read : — On a new- 

 oxide of tellurium, by Dr. E. Divers and M. Shimose. When 

 the compound of sulphur trioxide and tellurium, discovered 

 almost simultaneously by the authors and by Weber, is treated 

 in a vacuum, sulphur dioxide is evolved and a new oxide of 

 tellurium is formed containing one atom of tellurium to one 

 atom of oxygen. The decomposition takes place between 180 

 and 230°. The oxide is black, and quite stable at ordinary 

 temperatures in dry air. No compound of this monoxide has 

 yet been prepared, but in its properties it is essentially different 

 from a mixture of tellurium and dioxide. — On tellurium sulph- 

 oxide, by Dr. Divers and M. Shimo-e. The authors prepared 

 this compound by pouring sulphur trioxide on to tellurium finely 

 powdered and dried. It was purified from sulphur trioxide by 

 heating to 35° and exhausting with the Sprengel pump. It is a 

 red amorphous solid, quite stable at ordinary temperatures in 

 sealed tubes. When heated in a vacuum to 90° it is changed 

 into a bright fawn coloured modification. — On a new reaction of 

 tellurium compounds, by Dr. Divers and M. Shimose. When 

 sulphuric acid containing a small quantity of tellurium dioxide 

 or sulphate in solution is poured into a hydrogen-generating 

 apparatus, and the escaping hydrogen passed through a second 

 portion of the telluretted sulphuric acid, a beautiful red colour, 

 due to tellurium sulphoxide, is rapidly developed. — On a simple 

 modification of the ordinary method for effecting the combustion 

 of volatile liquids in Glaser's furnace with the open tube, by 

 Watson Smith. The author causes the end of the combustion 

 tube to project from the furnace, and volatilises the liquid by 

 gently warming the current of gas with a Bunsen burner. — On 

 the production of ammonia from the nitrogen of minerals, by 

 G. Beiloy. The author gives the results obtained with typical 

 oil and coal shales when distilled (1) at a low red heat, (2) at a 

 low red heat in a current of steam, (3) at a low red heat in a 

 current of steam, the residual coke being afterwards subjected 

 to the prolonged action of steam, so that a large portion of the 

 coke is consumed and the nitrogen in it liberated as ammonia. 

 Thus a sample of oil shale furnished by (1) 2-7 lbs. of nitrogen 

 per ton as ammonia, by (2) 3-9 lbs., by (3) 12'olbs. — On the 

 specific gravity of paraffin wax, solid, liquid, and in solution, 

 by G. Beilby. 



Zoological Society, May 1.— Prof. W. H. Flower, F.R.S., 

 president, in the chair. — The Secretary read an extract from a 

 letter addressed to him by Mr. W. L. Crowther, C.M.Z.S., 

 respecting the possibility of obtaining living specimens of the 

 Thylacine of Tasmania. — The Secretary exhibited, on behalf of 

 Mr. H. Whitely, the skin of a Bird of Paradise (Diphyl- 

 lodes gulielmi) from the Island of Waigiou, which was believed 

 to be the second example of this rare species yet obtained. — The 

 Secretary exhibited a set of Radde's international colour-scales, 

 and explained the way in which it was intended to be used. — A 



