164 Microscopical Essays. 



above the furface of the glals. When it is fo difpofed, hold it as- 

 level as you can over the clear part of a fire that is not too fierce, 

 or over the flame of a candle, at a diftance proportionable to the 

 degree of heat it requires, (which experience only can dire 6V) and 

 watch it very carefully till you difcover the faline particles 

 beginning to gather and look white, or of fome other colour, at 

 the extremities of the edges ; then having adjufted the microfcope 

 before-hand for it s reception, armed with the fourth glafs, which 

 is the fitteft for moll of thefe experiments, place it under your 

 eye, and bring itexaclly to the focus of the magnifier; and after 

 running over the whole drop, fix your attention on that fide 

 where you obferve any increafe or pufhing forwards of cryftalline 

 matter from the circumference towards the center. 



This motion is extremely flow at the beginning, unlefs the drop 

 has been over-heated, but quickens as the water evaporates, and 

 in many kinds, towards the conclufion, produces configurations 

 with a fwiftnefs inconceivable, compofed of an infinity of parts, 

 which are adjufted to each other with an elegance, regularity, 

 and order, beyond what the exafteft pencil in the world, guided 

 by the ruler and compafs, can ever equal, or the raoft luxuriant 

 imagination* fancy. 



When aclion once begins, the eye cannot be taken off, even 

 for a moment, without lohng fomething worth obfervation ; for 

 the figures alter every inflant, till the whole proeefs is over; and 

 in many forts, after all feems at an end, new forms arife, different 

 entirely from any that appeared before, and which probably are 

 owing to fome final I quantity of fait of another kind, which the 

 other feparates from, and leaves to a6l, after itfelf has done ; and 



