14 PHILOSOPHICAL TRANSACTIONS. [aNNO 1 683-4. 



snowy season, but less in a frosty, clear, and dry one, as also more in a cold 

 than in a warm air. When the wind was northerly, or easterly, the gain was 

 less, caeteris paribus, than when southerly or westerly, and less in the day than 

 in the night. The primary cause of this phenomenon seems to be the moisture 

 of the air, which our liquor greedily imbibes. And we may safely conclude that 

 moisture is the chief and only cause of the increase of weight in oil of vitriol, 

 since in dry clear weather it constantly increases less than in moist and cloudy, 

 the circumstance of heat or cold remaining the same in both. 



As to the quantity of the whole increase, it cannot be determined by any 

 general rule, since it varies according to the different strength of the oil of 

 vitriol : for it appears by the table, that the more diluted the liquor, the less 

 attractive it proved. This here employed, which was highly phlegmated, gave a 

 triple and more than -J- of its first weight, amounting in all from 3 to 9 drams, 

 and 30 grains, before it came to a stand. Which proportion of increase I found 

 confirmed in less quantities also; as 3 grains increased to more than 9 grains; 

 and 1 grain gave the weight of something more than 3 grains. But besides the 

 strength of the liquor, there are other circumstances; as the season of the year, 

 and position of the place, which will certainly cause some alteration : thus, our 

 liquor will gain more in winter than in summer ; more in a cellar and sunless 

 room, than in a room not so qualified. 



All these circumstances, which relate to the quantity, will also influence very 

 much the time of the increase ; but what makes the most peculiar and principal 

 variation in this point, is the proportion of the surface to the bulk of the liquor ; 

 for the greater or less the surface is, the quicker or slower is the increase. 

 Thus, 3 grains dropped and diffused to nearly ^ of an inch in breadth on a piece 

 of glass, gained 3 grains in 6 hours, 1 grain in 6 more, 1 grain and -i- in 12 

 hours more, in the next 12 hours it gained -|- a grain, and in the last 12 hours it 

 gained very little observable. So that in less than 48 hours, having more than 

 triple its first weight, it was for sometime fully saturated, till rainy weather 

 added something more. But to discover more nicely what influence the propor- 

 tion of surface has in promoting or retarding the increase of weight, I exposed 

 in the same room, and to the same temper of the air, 3 drams of the same oil 

 of vitriol, in an open flat glass, 1 inch broad, being only J- of the diameter of 

 that glass used at first with the like quantity. The result was, that whereas the 

 other surface, of 3 inches diameter, gained, as in the table, near 1 9 grains the 

 first 6 hours, this less surface gained a very little perceivably more than 2 grains 

 in the same time. Now since the areas of circles are to one another as the 

 squares of their diameters; as I the square of the less, is to 9 the square of the 

 greater diameter ; so was the weight of a little more than 2 grains, gained in 



