HOOKE 139 



Hooke used glasses " of our English make " ; his com- 

 pound microscope is figured. The body, probably of 

 brass, was 6-7 in. long, and was screwed by means of a 

 ball-joint into a ring, which slid on an upright pillar. 

 The tube of the microscope could be moved in any 

 direction ; the object was fixed to a jointed arm. The 

 unsteadiness of the arrangements must have been a 

 great hindrance to work. Sunlight, diflfused daylight or 

 lamplight was used, the light being reflected, if required, 

 from paper or ground glass. A glass globe filled with 

 water or brine served as a condenser ; a sub-stage 

 condenser is also shown, which consists of a conical 

 tube capable of being filled with water and provided 

 with a plano-convex lens at each end. 



The following passage from the Micrographia shows 

 how the simple microscopes, which were to play so great 

 a part in the natural history investigations of the next 

 two hundred years, were first made. " Could we make 

 a Microscope to have only one refraction, it would, 

 ccBteris paribus, far excel any other that had a greater 

 number. And hence it is, that if you take a very clear 

 piece of a broken Venice glass, and in a Lamp draw it 

 out into very small hairs or threads, then holding the 

 ends of these threads in the flame, till they melt and 

 run into a small round Globul, or drop, which will hang 

 at the end of the thread ; and if further you stick 

 several of these upon the end of a stick with a little 

 sealing Wax, so as that the threads stand upwards, and 

 then on a Whetstone first grind off a good part of them, 

 and afterward on a smooth Metal plate, with a little 

 Tripoly, rub them till they come to be very smooth ; if 

 one of these be fixt with a little soft Wax against a 

 small needle hole, prick'd through a thin Plate of Brass, 

 Lead, Pewter, or any other Metal, and an Object, plac'd 



