TRANSACTIONS OF SECTION A. 275 



The two bodies, the comet and the planet, will of course in time, if undisturbed, 

 come back again to the place from which they parted company. The comet will 

 here undergo a new disturbance, perhaps pass close behind the planet and be 

 thrown out into the stellar spaces again. 



Some comets will by reason of smaller perturbations have their orbits so 

 changed as to no longer come back to the appointed place of meeting, and these 

 may become more or less permanent members of the solar system. 



_ This conclusion suggests the possibility that the asteroids have also an outside 

 origin. If a comet were to be brought to move in a nearly circular orbit at a dis- 

 tance from the large planets, and it is probably only such an orbit that can be 

 really permanent, then the action of the sun by which the comet's tail is developed 

 ought in the course of time to drive off all the matter that makes the comet's 

 tail and leave the exhausted nucleus to travel in its orbit as a small planet. 



If in like manner we can suppose a like origin for some of the satellites, we 

 may be relieved of our difficulty. I cannot conceive how such small bodies can 

 become solid from a gaseous state in the immediate presence of the sun and the 

 large planets. 



A possible explanation of the lenticular form of the zodiacal light and its near 

 coincidence with the ecliptic is alike suggested. That body may be matter in 

 very minute parcels which has been thrown into this position by the action of the 

 planet Jupiter. 



5- On Self-acting Intermittent Siphons and the Conditions which Determine 

 the Commencement of their Action. By Rogers Field B A — See 

 Reports, p. 223. 



b. A short Account of some Experiments made to determine the Friction of 

 Water upon Water at low Velocities. Bu the Rev. Samuel Haughton 

 M.D., D.C.L. 



A spherical ball of granite, unpolished, was suspended by a pianoforte wire, and 

 allowed to hang freely ; from the brass collar, by which the ball was suspended an 

 index projected on each side, the pointed ends of the indices traversing a graduated 

 horizontal circle, whose centre corresponded with the line of suspension. °Tke sus- 

 pended ball was immersed in water contained in an iron tub. 



The weight of the granite ball was 22452-85 grams, and its mean diameter was 

 2ol-46 millimeters. The length of the wire of suspension was 610-8 centimeters, 

 and its diameter was 0-889 millimeter. The diameter of the iron tub was 2 feet 

 4 inches, and the depth of water contained in it was 1 foot 9 inches. 



The method of observation was as follows : the indices of the ball havin°- arrived 

 at the zero of rest, the ball was then displaced by a torsional movement of the wire 

 and allowed to regain its position of rest by a succession of vibrations, of diminish- 

 ing amplitudes. 



The quantities observed were the time of vibration and the rate of diminution of 

 the amplitude. 



The equations of motion of the apparatus are thus found. 



(Px -,. 



** ° (1) 



where x = the varying amplitude of any point of the surface of the ball measured 



iromits zero of rest. 



X = the tangential forces of torsion and friction acting at the point v 



It we assume that for low velocities the friction wiU be proportional to the 



velocity, we shall have 



X = k\v -ffo 



J dt (2) 



T 2 



