French Xationcl Institute. £?73 



We have already heard how rich the harvest of this year 

 has been in the science of nature : the zeal of the mathe- 

 matical department has not been wonse supported, nor le?-i 

 fortunate. Even those of our fellow-members who had the 

 greatest right to enjov in tranquillity the renown acquired 

 by a long series of labours, have not shown le-s ardour or 

 less activity. 



Thus, in the question started oii the subject of the new 

 measure of the degree in Lapland, when it was necessary to 

 discover the cause of the error which had been committed 

 in 1736, M. Lalande has sought, during the course of long 

 experience, facts which might pat us in the way of the de- 

 sired explanation. He recollected that at this time the use 

 of the proving telescope was entirely unknown. This in- 

 strument, so convenient and so simple, which was supposed 

 to be invented about the same time as the application of te- 

 lescopes to sectors and quadrants, is more modern, how- 

 ever, th.-tn we thought : we make use of it every day, as is 

 too often the case, without inquiring to whom we are in- 

 debted for it. It is mentioned for the first time in M. La- 

 landc's Astronomy, in the edition of 1764. In order to adjust 

 the parallelism of the telescopes, Bouguer recommended the 

 use of two little pins, which might reciprocallw change places^ 

 to ascertain whether they really had the same height. He 

 himself made use of a more imperfect method. and which mav< 

 still less than the pins, enter into comparison with M. La- 

 lande's proving telescope, so universally adopted at present. 

 We are uncertain whether Graham had any thing equivalent 

 to thi^ for adjusting his sector : Maiipertuis makes no men- 

 tion of it in the chapter v.here he treats of the acljus:ment of 

 this instrument J and this negligence may partly explain the 

 error wliich is imputed to him. 



This same measure of the degree in Lapland has giverx 

 occasion to M. Lalande to furnish us with another memoir, 

 where he demonstrates the necessity of attending to the 

 oblateness of the eartli in the operations of levelling which 

 reach to anv considerable distances. 



The attention of all the astronomers of Paris was given to 



ilie fclipsc of the l6th of .fune last. To M. Messier, one 



S 2 K>\ 



