146 



NATURE 



\7wie 21, 1877 



there were, as well as those of M. Peaucellier and Mr. 

 Hart, all particular cases of linkworks of a very general 

 character, all of which depended on the employment of 

 a linkage composed of two simil.ir figures. I have not 

 sufficient time, and 1 think the subject would not be suffi- 



ciently inviting on account of its mathematical character, 

 to dwell on it here, so I will leave those in whom an in- 

 terest in the question has been excited to consider the 

 original paper. 

 At this point the problem of the production of straight- 



line motion now stands, and I think you will be of opinion 

 that we hardly, for practical purposes, want to go much 

 farther into the theoretical part of the question. The 

 results that have been obtained must now be left to the me- 

 chanician to be dealt with, if they are of any practical value. 



I have, as far as what I have undertaken to bring before 

 you to-day is concerned, come to the end of my tether, 

 i have shown you that we r(?« describe a straight line, and 

 ho-iU we can, and the consideration of the problem has 

 led us to investigate some important pieces of apparatus. 



But I hope that this is not all. I hope that I have shown 

 you (ard )Our attention makes that hope a beliel) that this 

 new field of investigation is ont possessing great intei est and 

 importance. Malhematiciarss have no doubt done much 

 more than I have been able to show you to day, but the 



unexplored fields are still vast, and the earnest investi- 

 gator can haidly fail to make new discoveries. I hope 

 therefore that you whose duty it is to extend the domain 

 of science will not let the subject drop with the close of 

 my lecture. 



BIOLOGICAL NOTES 



The Tickorhine Rhinoceros. — A number of the 

 Memoirs of the Imperial Academy of Sciences of St. 

 Petersburg just issued contains an elaborate article on 

 the Tichorhine Rhinoceroses by the veteran naturalist, 



Dr. J. F. Brandt. Dr. Brandt treats of two extinct 

 species under this category, which he calls R. aiitiquilatis 

 (i.e., R. tiiiwrliums, auctt.) and R. nierkii. With the latter 

 he proposes to unite R. t'lniscus of Falconer. Remaiks 

 are added upon A". Icptorliinus of Cuvier and other allied 

 species. When we consider the number of valuable con- 



