Microscopical Essays. 



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the flame. When a large globule is forming, it mould be gently 

 agitated by making the tripoli, which will prevent it's becoming 

 flat on one fide. By attending to thefe directions, the greater 

 part of the globules will be round and fit for ufe. In damp wea- 

 ther, notwithstanding every precaution, it will often happen, that 

 out of forty globules, f our or five only will be fit for ufe. 



Mr. Stephen Gray, of the Charter-Houfe, having obferved 

 Tome irregular particles within a glafs globule, and finding that 

 they appeared diftinft and prodigioufly magnified when held clofe 

 to his eye, concluded that if he placed a globule of water, in 

 which there were any particles more opake than the water, near 

 his eye, he mould fee thofe particles diftin&ly and highly mag- 

 nified. This idea, when realized, far exceeded his expectation. 

 His method was, to take on a pin a fmall portion of water which 

 he knew had in it fome minute animalcules ; this he laid on the 

 end of a fmall piece of brafs wire, till there was formed fomewhat 

 more than an hemifphere of water ; on applying it then to the 

 eye, he found the animalculae moft enormoufly magnified ; for 

 thofe which were fcarce difcernible with his glafs globules, with 

 this appeared as large as ordinary fized peas. They cannot be 

 feen by day-light, except the room be darkened, but are feen to 

 the greater!: advantage by candle-light. Montucla obferves, that 

 when any objects are inclofed within this tranfparent globule, 

 the hinder part of it acts like a concave mirror, provided they be 

 fituated between that furface and the focus ; and that by this 

 means they are magnified three times and a half more than they 

 would be in the ufual way. An extempore microfcope may be 

 formed, by taking up a fmall drop of water on the point of a pin^ 

 and placing it over a fine hole made in a piece of metal ; but as. 



