SCIENTIFIC NiWS. f9 



SCIENTIFIC NEWS. 



NATIONAL INSTITUTE - OF FRANCE. 



Extract of the Report of the Tranfaclians of the Clafs of Mat he- French National 

 matical and Phj/fical Sciences, during the laji. Trimejlre of the In i titutc » 

 Year 9. 



Mathematical Part. By Citizen Delambre. 



Memoir on the Equilibrium -of Arches. By C I t . Bo s s u t . Boflut on 



arches* 



A. . 

 S the key ftones of which an arch is corrrpofed, Support 

 themfdves by mutual equilibration, and remain fufpended 

 without the aid of any fupport beneath, their whole force di- 

 recting itfelf againft the buttreffes ; in order to enfure the 

 duration of an arch, it is not fufficicnt that all its key-ftones be 

 in equilibrio ; but it is neceuary that its fupports at the ends 

 fliould oppofe a reii fiance adequate to the force which it exerts 

 in order to overthrow or break them in pieces. . • 



The enquiry refpecling the means proper for preventing 

 their being overthrown, conftitutes what is termed the pro- 

 blem of the lateral preflure of arches. Several geometricians 

 of the laft century had already occupied themfelves with this 

 fubjeel, but they had intirely neglecled to inquire into the 

 means of preventing theie fupports from being crufhed. 



C. BotTut undertook, in the year 1770, to treat the queftion 

 in the moil general manner, as well for limple arches as 

 domes. He has inveftigated whatever relates to the figure 

 and the lateral preffure of vaults. His memoirs have been 

 printed in the volumes of the Academy of Sciences for the 

 years 1774 and 1776. 



After many new obfervations and various experiments, 

 which may be of the greateft practical utility, C. Boflut has 

 refumed the fubjeft of his two memoirs. He has new mo- 

 delled them by fimplifying his calculations in feveral places, 

 and has made a number of additions relative both to theory 

 and practice ; fo that the whole, in its prefent ftate, confti- 

 tutes a work that may be confidered as original. 



Comets. — C. Meflier has read an account of the comet Comet of July 

 which he difcovered on the 23d of Meffidor laft, about half an la > l8ou 



hour 



