'French National Irjlilute. &oJ 



than at any period ever remembered. According as we follow 



the one or the other of the two authors above mentioned, the 



difference will be 16 or 48 



C. Meiflier read alfo a note on the eelipfe of the moon 



which took place on the fhft of October lad. The clouds 



prevented him from obferving the commencement of it. 



Tov trds the middle the moon appeared at certain intervals; 



and he took advantage of thefe moments to meafure twelve 

 times the part eclipfed. At u h. 21't'ic eelipfe feemed to 

 be at an end : it was more certainly fo at 1 1 h. o' 40". Ac- 

 cording to the observations of C. Delambre, the end took 

 place about u h. c/ 30"; which agrees pretty weii with what 

 might have been expected. 



C. Prony read a memoir containing a defcription and the 

 analytical theory of a new in fl rumen t, proper for meafuring 

 the length of a pendulum that fwings feconds. It is well 

 known, that the uiual method requires the niceft attention, 

 not only in regard to the form of the body made to ofcillate, 

 but alfo that the ofcillations may not be prolonged beyond 

 two hours at mod, and that the refults deduced from them 

 may be always fubordinate to the regularity of the time-piece 

 which ferves for comparifon ; and in the lad place, the ne- 

 celfity of fitting up, and taking to pieces the apparatus, may 

 leave fome doubts refpecYing the identity of the experiments 

 made at different times, and in different places. All thefe 

 inconveniences C. Prony propofes to remedy. His new inftru- 

 nient fuperfedes the neceffity of paying attention to the form 

 of the ofcillating body ; the ma Is of it is too considerable for 

 the ofcillations to continue during the whole time that 

 elapfes between two confecutive pafiages of a ftar over the 

 lame vertical, fo that the time-piece of comparifon is of no 

 further ufe than to count with more facility the ofcillations 

 jof the pendulum ufed for the experiment. 



The theory of C. Prony appears to be clear and fatisfac- 

 tory, and he foon intends to fubjecl: his new pendulum to a 

 trial. The ingenious method by which Borda found means 

 to correct or obviate the inconveniences of the common 

 method are not yet forgotten. His determination of the 

 length of the pendulum received the approbation of all 



learned 



