$40 COSMOS. 



tect view was taken up by Halley late in the eighteenth 

 century, and was then more fully and satisfactorily explained 

 with reference to the action of the velocity of rotation pe- 

 culiar to each parallel of latitude. Halley, prompted by his 

 long sojourn in the torrid zone, had even earlier (168G) pub- 

 lished an admirable empirical work on the geographical ex- 

 tension of trade winds and monsoons. It is surprising that 

 he should not have noticed, in his. magnetic expeditions, the 

 law of rotation of the winds, which is so important lor the 

 whole of meteorology, since its general features had been rec- 

 ognized by Bacon and Johann Christian Sturm, of Hippol- 

 steiu (according to Brewster, the actual discoverer of the 

 differential thermometer*). 



In the brilliant epoch characterized by the foundation of 

 mathematical natural philosophy, experiments were not want- 

 ing for determining the connection existing between the hu- 

 midity of the atmosphere, and the changes in the tempera- 

 ture and the direction of the winds. The Accademia del 

 Cimento had the felicitous idea of determining th^quautity 

 of vapor by evaporation and precipitation. The oldest Flor- 

 entitle hygrometer was accordingly a condensation-hygrome- 

 ter an apparatus in which the quantity of the discharged 



avesse neeessita d'obbedire al suo moto, se noil in quanto 1' asprezza 

 della superficie terrestre ne rapisce, e seco porta una parte a se contigua, 

 che di non molto intervallo sopravauza le maggiori altezze delle niou- 

 tague ; la qual pozzion d'aria tanto meno dovra esser renitente alia 

 conversion terrestre, quanto che ella e ripiena di vapori, fumi, ed esala- 

 zioni, materie tutte participant! delle qualita terrene: e perconseguen- 

 za atte naie per lor natura (?) a i medesimi movimeiiti. Ma dove, man- 

 cas.sero le cause del moto, eioe dova la superficie del globo avesse grandi 

 spazii piani, e ineno vi fusse della mistione de i vapori terreni, qnivi ces- 

 6erebbe in parte la causa, per la quale 1' aria ambieute dovesse total- 

 mente obbedire al rapimento della conversion terrestre ; si che in tali 

 uoghi, meiitre che la terra si volge verso Oriente, si dovrebbe sentir con- 

 tiuuamente un vento. che si ferisse, spiraudo da Levante verso Ponente; 

 e tale spiraineuto dovrebbe farsi piu sensibile, dove la vertigine del 

 globo fusse piu veloce : il che sarebbe ne i luoghi piu remoti da i Poli, 

 e vicini al cerclno massimo della diurna conversione. L'esperienza ap- 

 plaude molto a questo filosofico discorso.poiche ne gli ampi mari sotto- 

 posti alia Zona torrida. dove anco l'evaporazioni terrestri mancano (?) 



si sente una perpetua aura muovere da Oriente " 



* Brewster, in the Edinburgh Journal of Science, vol. ii., 1825, p. 145. 

 Sturm has described the Differential Thermometer in a little work, en- 

 titled Collegium Experimentale Curiosum (Nuremberg. 1676), p. 49. 

 On the Baconian law of the rotation of the wind, which was first ex- 

 tended to both zones, and recognized in its ultimate connection with 

 the causes of all atmospheric currents by Dove, see the detailed treatise 

 of Muncke, in the new edition of Gehler's Physikal. Worterbuch, bd 

 x., s. 2003-2019 and 2030-2035. 



