1881. J on the Distances of the Stars. 519 



firms tlio first. Measurements of the position angle were also made 

 at the same time. Some difficulties not yet fully explained have 

 arisen, but on the whole the measurements of the positive angle seem 

 to confirm the supposition that the parallax of Groombridge 1G18 is 

 about one-third of a second. No doubt this is but a small quantity. 

 The orbit of the earth viewed from Groombridge 1G18 is about the 

 same size as a pcnny-jjioce at the distance of seven miles. 



Proper Motions of the Stars. 



Geologists have made us acquainted with the enormous intervals of 

 time which have elapsed since the earth first became the abode of 

 living animals. Regarding a period of 50,000,000 of years as com- 

 parable with geologic time, some considerations were adduced as to the 

 efiect of 2^roper motions during such an interval. It was pointed out 

 that in all probability none of the stars now visible to the unaided eye 

 can have then been visible from the earth. 



The Nature of Space. 



The possible connection of parallax work with the problems of the 

 nature of space was then alluded to. It was shown that if space be 

 hyperbolic the observed parallax is smaller than the true parallax, while 

 the converse must be the case if space be elliptic. The largest triangle 

 accessible to our measm*ements has for base a diameter of the earth's 

 orbit, and for vertex a star. If the defect of such a triangle be in any 

 case a measurable quantity, it would seem that it can only be elicited 

 by observations of the same kind as those which are made use of ia 

 parallax investigations. 



[K. S. B.] 



WEEKLY EVENING MEETINGS. 



Friday, February 18, 1881. 



Thomas Boycott, M.D. F.L.S. Vice-President, in the Chair. 



Sir John Lubbock, Bart. M.P. D.C.L. F.R.S. M.B.I. 



Fruits and Seeds. 



(The Discourse, with Illustrations, will be given in the next number of the 

 Proceedings^ 



Friday, February 25, 1881. 



Thomas Boycott, M.D. F.L.S. Vice-President, in the Chair. 



Dr. J. S. Burdon Sanderson, LL.D. F.R.S. 



Excitahility in Plants and Animals, 



(Abstract deferred.) 



