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Microscopical Essays. 



pared his glafs by beating it to powder, and wafhing it very clean; 

 he then took a little of this glafs upon the lharp point of a filver 

 needle, wetted with fpittle, and held k in the flame, turning it 

 about till a glafs ball was formed ; then taking it from the flame, 

 he afterwards cleaned it with foft leather, and fet it in a brafs 

 cell. 



No perfon has carried the ufe of thefe globules fo far as T. Di 

 Torre, of Naples, nor been fo dexterous in the execution of 

 them ; and if others have not been able to follow him in the fame 

 line, it may be fairly attributed to a want of that delicacy of 

 touch for adj lifting the objects to their focus, and that acutenefs- 

 of vifion which can only be acquired by long practice. P. Torre 

 has alfo defcribed, more minutely than any other author, the 

 mode of executing thefe globules, which, as it throws much light 

 upon the preceding defcription by Dr. Hooke, will not, it is pre- 

 fumed, be unacceptable to the reader. 



Three things are neceffary for forming of thefe globules t 

 i . A lamp and bellows, fuch as are ufed by the glafs-blowers ; 

 2. A piece of perfect tripoli; 3. A variety of fmall glafs rods.. 

 \Vhen the flame of the lamp is blown in an horizontal dire&ion, 

 it will be found to confift of two parts ; from the bafe to about 

 two-thirds of it's length, it is of a white colour ; beyond this, it 

 is tranfparent, and colourlefs. It is this tranfparent part which 

 is to be ufed for melting the glafs, becaufe by this it will not be 

 in the leaft fullied ; but it will be immediately foiled, if it touches 

 the white part of the flame. The part of the glafs which is pre- 

 fented to the flame, ought to be exceeding clean, and great care 

 fhould be taken that it be not touched by the fingers. If the 

 6 g lafs 



