TRANSACTIONS OF THE SECTIONS. 



23 



under high magnifying power, a minute portion on the surface next the telescope 

 was found to have been completely melted, a small pimple surrounded by a hollow 

 having been formed. Six or seven dark glasses have been destroyed m the same 

 way ; not one has been broken, all having had the small portion of the surface melted. 

 Latterly this accident has been prevented from recurring by placing the dark glass 

 closer to the telescope. ^ 



On M. Guyot's Experiment. By the Rev. Professor Powell, F.R.S. ^c. 

 The recent experiment of M. Foucault, giving direct proof of the earth's rotation, 

 having excited so much attention, it seems remarkable that an equally striking one 

 devised and tried by M. J. Guyot in 1836, should have been passed over or forgotten. 

 That gentleman conceived, that as a falling body deviates to the east, a long plumb- 

 line ought to do the same. This experiment he performed in the dome of the Pan- _ 

 theon at Paris, with a plumb-line about 172 feet long, and determined the deviation 

 to be 4 J millims. in 57 metres. His mode of experimenting was by small balls, one at 

 the point of suspension, the other at the weight, whose images, strongly illuminated 

 and reflected in a basin of mercury placed below, were viewed from above and found 

 to coincide, when the eve was laterally distant 4i millims. from the upper ball. The 

 experiment might probably be simplified without the trouble of illumination, by 

 making the suspension from a pin passed across a small circular aperture in a flat 

 roof, the light coming through, which would probably give a sufiiciently light image 

 in the mercury below. The' effect is also stated to be sufficiently perceptible with 

 much less length. But much doubt has been expressed with respect to i\ie principle. 

 It seems, therefore, desirable that attention should be drawn to the question. 



Communication respecting the Comet of Short Period discovered by Brorsen, 

 February 26, 1846, and its reappearance in 1851. By Dr. Von Galen. 

 Of the different heavenly bodies which made their appearance in the year 1846, 

 the comet discovered by Brorsen, February 26, merits our special attention, on ac- 

 count of its short period of revolution round the sun. 



From fifty-five of the best observations made on this comet, in which are included 

 the two observations made at the Greenwich observatory, I have determined the 

 following fundamental positions. 



Mean time, Greenwich. 

 1846. 



Feb. 33-924600 

 „ 44-029902 

 „ 50-990194 

 „ 57-495320 

 „ 80-976101 



Comet's right Ascen- 

 sion. 



12 54 36-40 



8 26 43-33 



1 44 47-14 



351 12 52-81 



260 5 27-57 



Comet's Declination. 



N. 26 33 105 

 43 30 48-14 

 54 28 51-06 

 63 25 33-63 

 71 2 29-00 



acdence by the method of least squares found the most probable elements to be : 

 Perihelion passage, 1846, Feb. 25-423919, mean time Greenwich. 



O I II 



Longitude of the perihelion, w 1 16 28 37-71 \ Mean deg. 



ascending node, ft . . 102 34 12-92 J Feb. 26. 



Inchnation of orbit, t 31 1 1-86 



Angle of excentricity, <^ 52 46 13-57 



Mean daily sidereal motion, /i 623-0164 



Log. semiaxis majoris. Log. a 0-5036714 



Motion Direct. 



Taking departure from these elements, I ascertained the perturbations produced by 

 the principal planets of the solar system on the comet, and with regard to these 

 pertiu-bations, got the following system of elliptical elements for its next appearance : 



