600 PHILOSOPHICAL TRANSACTIONS. [aNNO I/AQ. 



along them, Mr. S. apprehends that he equally neglected examining the plant 

 with proper glasses. Perhaps he adopted the term capillaris from professor Van 

 Royen's Synouyme, which he quotes ; especially since, in his divisions and spe- 

 cific characters of the conferva, he has fallen into the same mistakes with Dille- 

 nius, whom he chiefly followed in his class of the Cryptogamia. If the systema- 

 tical botanists have not therefore acquired an adequate knowledge of the 

 structure of the minuter confervas, by neglecting to use proper glasses, their 

 descriptions of these plants must necessarily be imperfect. 



The specimens of paper, which Mr. S. sent with the copy of his letter, are, 

 1st. A specimen of the natural paper of cortona. 2dly. An artificial paper 

 made of the same substance with the natural paper of cortona ; which substance 

 he proved to be the common conferva. 3dly. A specimen of a much better and 

 stronger paper made of the same conferva, by Sir Alexander Dick, baronet, near 

 Edinburgh. 4thly. A specimen of another artificial paper, which Mr. S. made 

 of the genista juncea macerated in warm water, and prepared afterwards in the 

 common manner. 



IX. Experiments on the Lateral Force of Electrical Explosions. By Joseph 



Priestley, LL. D., F. R. S. p. 57- 



Dr. P. being informed, in accounts of damages done by lightning, of persons 

 and things being removed to considerable distances, without receiving any hurt, 

 he was excited to try whether he could produce similar effects by electricity. All 

 the other known effects of lightning had been frequently imitated by the appli- 

 cation of this power ; but he did not know that this effect had ever been taken 

 notice of by any electrician. The experiments he presently found to be very 

 easy ; and he thinks it not difficult to ascertain the cause of this striking effect, 

 and the manner in which it is produced. 



If pieces of cork, wood, powder of any kind, or any light bodies whatever, 

 be placed near the explosion of a jar, or battery, they will not fail to be moved 

 out of their places, at the instant of the discharge. If the explosion of a large 

 battery be made to pass over the surface of animal or vegetable substances, in the 

 manner described in the printed account of his experiments, and large corks be 

 strewed along, or near the path intended for it, it is surprising to observe with 

 what violence they will be driven about the room ; and this dispersion is in all 

 directions from the centre of the explosion ; and it makes no difference whetlier 

 the rods, between which it is made, be sharp-pointed or otherwise. The effect 

 of this lateral force is very remarkable in attempts to fire gunpowder in electrical 

 explosions. If the gunpowder be confined ever so close in quills or cartridges, 

 and they be held fast in vices, yet, when the explosion is made in the centre of 

 them, it will sometimes happen, even when a wire has been melted in the midst 



