VOL. I.] PHILOSOPHICAL TRANSACTIONS. 1^$ 



near a quarter of an inch ; though, the weather being fair and calm, there ap- 

 peared no manifest change in the air ; and though also since that time the mer- 

 cury in the two instruments had for the most part risen and fallen together as 

 before. 



Mr. Boyle has observed the heights of the mercury to be greatest in droughts, 

 which he supposes owing to the elevation of steams from the earth, which may 

 gradually increase the weight of the atmosphere; for March 12, 1665-6, at 

 Oxford the quicksilver was higher than had been observ^ed in England, viz. 

 about -jV above 30 inches ; but upon the first considerable showers that inter- 

 rupted the long drought, he foretold many hours before, that the mercury 

 would be very low, and so he found it at Stanton to fall -f- below ig inches, 

 there being also a blustering wind with the rain. 



It is rather difficult to settle any general rule about the rising and falling of 

 the mercury ; yet in those parts one that seems to hold oftenest is, that when 

 high winds blow the mercury is lowest, and yet even this sometimes fails. 



General Heads for a Natural History of a Country, By Mr. Boyle, 



N' 11, p. 186. 



The things to be observed in such a history may be variously divided : As 

 into supraterraneous, terrestrial, and subterraneous. But we will at present dis- 

 tinguish them into those things that respect the heavens, or concern the air, 

 the water, or the earth. 



1. To the first sort of particulars belong the longitude and latitude of the 

 place, and consequently the length of the longest and shortest days and nights, 

 the climate, the parallels, &c. ; what fixed stars are, and what are not seen 

 there. 



2. Concerning the air, may be observed its temperature, as to the first four 

 qualities and the measures of them : its weight, clearness, refractive power ; 

 its subtilty or grossness ; its abounding with or wanting salts, its variations ac- 

 cording to the seasons of the year, and the times of the day ; what duration the 

 several kinds of weather usually have ; what meteors it mostly produces, and 

 in what order they are generated ; and how long they usually last ; especially, 

 what winds it is subject to ; whether any of them be stated and ordinary, &c. 

 What diseases are epidemical ; what is the usual salubrity or insalubrity of the 

 air ; and with what constitutions it agrees better or worse than others. 



3. Concerning the water, may be observed the sea, its depth, degree of salt- 

 ness, tides, currents, &c. Next rivers, their width, length, course, inundations, 

 goodness, lightness of waters, &c. Then lakes, ponds, springs, and especially 



