38t> PHILOSOPHICAL TRANSACTIONS. [aNNO I767. 



into which moisture can any way descend, we almost always find these kind of 

 crystallizations and concretions ; and the more plentiful the moisture is, and the 

 more porous the strata of earth or stones are through which it passes, the larger 

 the concretions are, and the more remote from a transparent state ; as appears in 

 those great caverns in the Peak, and in Somersetshire, &c. Whereas, on the 

 contrary, the harder and less porous the substance is, through which the moisture 

 passes, the more transparent are the stones formed by it, as in the case of Bristol 

 stones, and of some of those beautiful spars adjoining to veins of ore. 



Whether all kind of stones may not be formed in somewhat the same manner, 

 by the water carrying the stony particles to the same place, and their collecting 

 there together, by their mutual attraction, he leaves to others to determine ; but 

 he is much persuaded, that this may probably be the manner of the production 

 of spars and crystals ; and perhaps jewels, or precious stones, may grow just in 

 the same way ; and owe their perfection solely to their being composed of still 

 more minute salts, and more slowly ; whence we may conjecture, why it is so 

 rare to find large diamonds. Some of the Bristol stones are observed to have 

 a fine purple appearance, like an amethyst ; and it is well known, that sevjeral 

 sorts of spars are of various beautiful colours, by means of a mixture of mineral 

 particles, in which they have a distant resemblance of jewels ; and indeed they 

 seem so be very analogous to them in many respects. 



VT. Experiments with Catnphire. By Mr. Alexander, Surg, in Edinburgh, p. 65. 



As medical authors have differed so widely in their opinions concerning the 

 nature and effects of camphire, one part of them positively affirming that it heats 

 the body, and another asserting with the same confidence that it cools it ; Mr. A. 

 made the following experiments with it, in order, if possible, to clear up the 

 difficulty. 



If camphire was a heater, he concluded it would raise his pulse, and augment 

 his natural heat ; and therefore, previous to his taking it, he counted the num- 

 ber of pulsations in a minute, which were 68, and found that, in the space of 5 

 minutes, the mercury in Fahrenheit's thermometer rose 18 degrees by the heat 

 of the pit of the stomach. Having thus found the state of his pulse, and of 

 his natural heat ; he took 9j of camphire in a little of the pulp of tamarinds ; 

 and 20 minutes after he applied the thermometer to his stomach : the mercury, 

 in the space of 5 minutes, rose exactly 1 8 degrees, as it had done before taking 

 the dose, but his pulse beat only 66, which was 2 strokes less. Three quarters 

 of an hour after he had taken the camphire, he applied the thermometer again ; 

 in the same space of time, the mercury rose exactly the same as in the last trial, 

 but his pulse beat only 65, which was one stroke less, and 3 fewer than it had 

 done before he took the camphire. 



