58 REPORT — 1860. 



As to chemistry, it may be briefly noted that its phenomena seem capable of being 

 brought within the science of motion by deductions from the general conceptions of 

 a body as a system of moving molecules (specific heat), which, the motion at every 

 point being equal in intensity, is in a state of dynamic equilibrium; and of the 

 formation of compounds, as the formation of new states of dynamic equilibrium. 



A General Law of Rotation applied to the Planets. 

 By J. S. Stuart Glennie, M.A. 



The author directed attention to a table of elements which seemed to point to a 

 general law for the angular velocity of rotation of the planets ; though, of the many 

 formulae calculated, none had as yet given perfect accuracy. 



But these tables gave a new law connecting the angular velocities of revolution 

 with the distances. 



He referred the nullity of effect on the planets of the resisting medium which 

 shortens the periods of Encke's comet to a neutralization deduced from a hydrody- 

 namical theorem. 



Sound. 



On the Velocity of the Sound of Thunder. 

 By the Rev. S. Earnshaw, M.A. 

 The object of this paper was stated by its author to be, to solicit the attention of 

 observers to certain phenomena which seem to indicate that the velocity of the 

 sound of thunder is sometimes much greater than that of ordinary sound. He had 

 himself noticed a case where the sound followed close upon the flash of lightning, 

 though judging from the distance of the point struck (more than a mile) from him, 

 the interval between the flash and the sound should have been upwards of five seconds. 

 He stated also that Professor Montigny of Antwerp had communicated to him accounts 

 of similar instances noticed by himself and M. Raucoux, cure of Temploux. One in 

 particular was very remarkable. On a certain night last autumn, Professor Montigny 

 observed the lightning strike a farm at such a distance from him, that, according to 

 the received velocity of sound, more than fifteen seconds ought to have elapsed before 

 he heard the report, whereas it reached him in two seconds. This was confirmed 

 to him the next day by the cure of Temploux, who being at nearly the same distance 

 from the farm, heard the crack of the thunder in what he judged to be certainly not 

 more than two seconds from the descent of the electric fluid. The difference in this 

 case is so great between theory and observation, that errors of estimation of the time 

 cannot possibly account for it. The two observers were more than 4000 metres 

 apart. The author stated, that although there were in these instances such discre- 

 pancy between them and the received theory, he had communicated investigations to 

 the ' Philosophical Magazine ' with which they were in perfect agreement. But, 

 nevertheless, he hoped that some of the members of the Association would turn their 

 attention to these phenomena, in order that it might be definitely settled, whether 

 his theoretical deductions are, or are not, supported and confirmed by undoubted 

 facts. 



On the Triplicity of Sound. By the Rev. S. Earnshaw, M.A. 



The fundamental idea of this paper is the hypothesis of finite intervals. Setting 

 out from this, the author shows that the most simple elements of wave-motion are 



defined by the equation ~ =+k 2 x, x being the displacement of an aerial particle at 



any time t. If the radius of molecular action extend over a large number of parti- 

 cles, the method pursued by the author gives the velocity of ordinary sound 1130 

 feet. He also shows that the velocity of a thunder-clap must of necessity be greater 

 than that of ordinary sounds. There are two essentially distinct types of wave- 

 motion, corresponding to the two signs with which k- is affected in the above 

 equation; the upper sign belongs to the thunder type, and the lower to ordinary 



