[ 4oS ] 



But to exprefs thefe ratios in thermometrical meafures we muft 

 endeavonr to find the greateft heat of the equinoxitl day, taking 

 a mean of the heat of the morning at two o'clock, and the even- 

 ing, under the equator, or very near it; and this I find to be 88° 

 or 89^ of Fahr. (See Ulloa, Mem. Philofoph. p. 6') in the northern 

 hemifphere, on the 20th of March, on the ocean, to which in- 

 deed we muft confine ourfelves in this enquiry, and particularly 

 the Atlantic, for no uniformity can be expedted on land. 



It is uncertain what thermometer of Reaumur Ulloa employed, 

 whether the true or the falfe, and hence I place the heat at 88? of 

 Fahr. 



This correfpondence being found, the thermometrical degrees 

 correfponding with all the other ratios are eafily found by the 

 rule of proportion, and the degrees thus found I call the mathe- 

 matical temperature. Bat in moft cafes this temperature is far from 

 agreeing with the temperature really obferved ; and which I there- 

 fore call the real temperature ; this I take at a mea?i, and not at 

 its maxiinum^ Vv'hich I could not always difcover, and is more fu- 

 gitive and contingent. Thefe temperatures I exhibit in two fe- 

 parate tables, the firft indicating thofe of the vernal equinox and 

 of the northern tropic or midfummer, and the fecond thofe of the 

 autumnal equinox and the fouthern tropic or midwinter, over the 

 Atlantic or ftandard ocean in our hemifphere. 



Table 



