37 



This apparatus, like the magnetic telescope of 

 s Prony, served me to determine the small ho- 

 rary variations of the magnetic variation, and 

 the intensity of the forces which change with 

 the latitudes. The oscillations of the great 

 magnetic dipping needle of Mr. Le Noir give 

 also a very exact measure of this last pheno- 

 menon. 



A magnetometer of Saussure*, constructed by Mr. 

 Paul at Geneva, with a limb that corresponds 

 to an arch of three feet radius ; 



An invariable pendulum, constructed by Mr. 

 Megnie, at Madrid; 



Two barometers by Ramsden ; 



Two barometrical apparatuses •jf, with the aid of 

 which we find the mean height of the barome- 

 ter, by successively plunging into a vessel se- 

 veral glass tubes, filled with mercury, closed 

 at one end by a steel screw, and placed in a 

 metal case ; 



Several thermometers by Paul, Ramsden, Megnie, 

 and Fortin ; 



Two hygrometers ofSaussure and Deluc, of hair 



and whalebone ; 

 Two electrometers of Rennet and Saxmure y of 



* This magnetometer, which I found inaccurate, the theo- 

 dolite, and reflecting circle, are the only instruments which 

 I could not embark with me at Corunna. 



+ I have described this apparatus in the Journal de Phy- 

 sique, t. xlvii, p. 468, and in my Observ. Astron. t. i, p. 366: 



