294? ATMOSPHERIC ELECTRICITY. 



Experiments their whole nutriment through the remaining part of the leaf- 

 and obfervations fta , L T[ did t however, acquire their full fize ; and the 

 on the motion of J ' ' 



the fap in trees, feeds were fmall, and, I think, incapable of vegetating ; but 



this I attribute to the want of nutriment in quantity rather than 

 in quality; for the union of the veflels of the leaf-ftalk with 

 thofe of the fruit-ftalk was very imperfect. The grapes, which 

 were the purple Frontigniac, poffefTed their mufky flavour, in 

 the fame degree with others growing on the fame plant. 



There is another experiment in my laft Paper, which I will 

 alfo notice here, becaufe it appears to lead to fome important 

 conclufions, and had been tried only in a tingle inflance. I 

 have there dated, that the ftem of a young tree became ellipti- 

 cal, by being confined to move only in the fegment of a large 

 circle. This experiment was fuccefsfully repeated during the 

 laft year, on other trees; but I have nothing to add to the de- 

 fcription which I have already given. 



I am, &c. 



T. A. KNIGHT. 



XIV. 



Extract of a Memoir of Mr. Erman, entitled, Obfenations 

 and Doubts concerning Atmofpheric Electricity *. 



IViR. ERMAN who is already fo advantageoufly known to 

 philofophers, has publifhed towards the end of laft year, a 

 memoir which appears to deferve their attention in an un- 

 common degree. 

 Signs of atmof- When he made experiments upon the electricity of the at- 



phenc eteftri- mofphere, he obferved a great difference between the refult 



city difrer ac- 



cording to the prelented by an electrometer armed with a conductor which 

 inftrument. was fucidenly raifed from the earth, according to the known 



method, and that of a metallic rod of much greater length which 



was initiated and fixed. 

 Defcription of The electrometer he ufed was that .diiTinguimed in 

 the eleflrometer. German y fy the name of the electrometer of Weifs. The 



length of its leaves of gold is half an inch, and the diameter 



of the glai's tube which enclofes them is three quarters of an 



journal de Phyfique, Thermidor 12, or Vol, LIX. 98. 



inch 



