400 ( Geological Society. 



When the inverse current passes, there is no contraction at the 

 beginning of the current, for the influence of this current upon the 

 nerve-current is one which antagonizes contraction ; when the inverse 

 current ceases to pass there is contraction, for then the influence 

 which antagonized contraction is removed. When, on the other 

 hand, the direct current passes, there is contraction at the beginning 

 of the current, for the influence of the current upon the nerve-current 

 is one which favours contraction ; when the direct current ceases to 

 pass, there is no contraction, for then the influence is no longer one 

 which favours contraction. 



(c) In the third period — that of single contraction — the muscular 

 movements resulting from the action of a galvanic current upon 

 nerve are at first sight somewhat perplexing; but with a little 

 thought, it may be seen that the same key will apply to their 

 interpretation. 



If, as has just been mentioned, contraction attends upon the 

 beginning of the direct current because this current is found to 

 favour contraction, it is not difficult to find a reason which will ex- 

 plain in some degree, not only why in the period of double contrac- 

 tion the strongest contraction is at the beginning of the direct 

 current, but also why in the first part of the period now under con- 

 sideration — that of single contraction — contraction should continue 

 to attend upon the direct current after it has ceased to attend upon 

 the inverse current. Nor are the apparent irregularities in contrac- 

 tion, the "voltaic alternatives," entirely inexplicable; for it may be 

 that these seeming irregularities — this apparent shifting of contrac- 

 tion from the beginning of the direct to the beginning of the inverse 

 current, and so backwards and forwards once and again — may be 

 nothing more than the natural consequence of the changes which at 

 this time have taken place, and are taking place, in the direction of 

 the nerve-current. 



" Letter from Lord Howard de Walden and Seaford, on a recent 

 severe Thunder-storm in Belgium." 



GEOLOGICAL SOCIETY. 



[Continued from p. 245.] 



June 13, 1860. — L. Horner, Esq., President, in the Chair. 



The following communications were read : — 



" On some Arrow-heads and other Instruments found with Horns 

 of Cervus megaceros in a Cavern in Languedoc." By M. E. Lartet, 

 For. M.G.S. (In a letter to the President.) 



In a cavern of the limestone at Massat, near Tarascon in Lan- 

 guedoc (Department of the Ariege), examined by M. A. Fontan, 

 the floor was found to consist of a blackish earth, with large rounded 

 pebbles, among which were mixed, in great disorder, bones and 

 horns of a Chamois, Cervus pseudovirginianus, C. megaceros, and Bos, 

 together with implements of stone and bone, to which MM. Isidore 

 GeofFroy Saint-Hilaire and E. Lartet have referred in the ' Comptes 

 Rendus ' of May 10, 1858. 



M. E. Lartet, in his letter, has furnished drawings and descriptions 



