390 Scientific Intelligence. — Mechanical Philosophy. 



perehelium would suffer only a periodical change ; and that the 

 nodes and the inclination of the orbit would not be altered. Li the 

 case of Encke's comet, the first two effects have been decidedly- 

 produced, and there are two circumstances to facihtate the calcula- 

 tion ; the first is, that this comet is always seen in the same point of 

 its orbit, and near to its perehelium ; and the second, that its orbit is 

 subjected only to very slow alterations. Both these circumstances 

 permit the supposition that the times of revolution (at least for some 

 periods) diminish by an equal quantity, so that their diminution may 

 be considered as proportional to the square of the times ; the period- 

 ical variation of the perehelium may also be neglected without incon- 

 venience. M. Encke supposes, with Newton, that the ether or re- 

 sisting medium, is diffused through all space ; that its density dimin- 

 ishes in the inverse ratio of the square of the sun's distance, and that 

 the resisting force is always proportional to the square of the actual 

 linear velocity of the comet. — Quar. Jour. Jul. — Sep. 1829. 



2. Brown's Active Molecules. — Mr. Holland, the inventor of a 

 microscope, sold by Carey of the Strand, has inclosed some of the 

 particles described by Mr. Brown, as active molecules, between glass 

 and talc, closing the whole hermetically, so as to exclude, as much 

 as care could do, all interference of external causes. Notwithstand- 

 ing this, the motion continued equally vivid even after ten days. The 

 lens used had a focus of the thirtieth of an inch ; and the particles 

 were obtained, as we understand, from gamboge. — Idem. 



3. Destruction of Vermin in ships, by steam. — By letters from In- 

 dia, it appears that the application of steam has been found wonder- 

 fully efficacious in cleansing ships from vermin, and especially the 

 white ant. A steam-boat {the Comet) was placed alongside a mer- 

 chant vessel, and steam from its boiler conveyed by a very simple 

 system of pipes, into the hold of the latter, the apertures to which 

 were closed as well as they could be. The operation was continued 

 for several hours, and there is no reason to believe that it was not ef- 

 fectual, and will prove a valuable process in the navy. Besides the 

 direct object of cleansing the ship, another advantage accrued, from 

 the discovery of every leaky place existing, by the oozing of the wa- 

 ter through them, in which way leaks were made manifest, that could 

 not be found out otherwise. The expense is said to be very mode- 

 rate ; and it is further stated to be the only process at present known, 



