Lclter from Von HumholJt to LaJande. ^6t 



cipal dclerminations of the longitude, which I made by means 

 of Eertboud's chronometer, from the obferved horary angles. 

 Cuniana, caftle of St. Antonio, lat. lo^ aj" 37" Long- weit. 



and (taking the long, of Madrid at 13° 58^) 46° 31'' 

 Puerto LIpana, in the ifland of Trinidad 43 49 30'' 



Tobngo, the eaftcm extremity - 42 47 30 



Macanao, the weil part of the ifland St. Margarita 46 35 30 

 Punto Araya, in New Andalulia - 4^ 35 3^ 



/(land of Cochc, eaftern extremity - 46 12 



Bncca de Drago ^not certain) - 44 23 



. Cabo de tres Puntas - - 44 54 30 



Caraccas a la Trinite 10'' 31' 4" latitude, very good. 



I fliall here alfo mention, that neither wind, ftorms, nor 

 the earthquake, have had the lead influence on' the regular 

 dailv variation in the Itate of the barometer; and that, ac- 

 cording to C. Richard, this daily variation amounts at Su- 

 rinam to two lines. 



Thcfeoblervarions are the more interefting, as all the charts 

 of this part of the world are very incorrcdl:; and the agree- 

 ment of mv longitude of TenerifF and Tobago, with the ob- 

 fervation? of Jjorda and Chabcrt, within from 2" to 5" of 

 time, is a proof of the excellence of my chronometers. 



The fcienity of the nights between the tropics gave me an 

 opportunity of comparing with each other the ilrength of the 

 light of the auftral ftars; which in fomc of them, fuch as 

 the Crane, Altar, Toucan, and the Foot of the Centaur, fecm> 

 to have changed fince the time of La Caille. I employed 

 the method propofed by Dr. Herfchcl, and diaphragms of 

 the fame kind as thofc ufcd for the fatcllites. If the light of 

 Sirius be fuppnfcd equal to ico parts, and that of Procyon 88, 

 the light of tlic following ilavi, according to my obfervation.s. 

 • are as below cxprefl'ed. 



LVllI. D*. 



