902 SEC. 20. COLLECTION OP APPARATUS AND PHOTOGRAPHS 



Thermometer, with balls in the shape of a little frog ; it 

 served, being tied to the arm, to determine the degrees of heat in 

 fever. 



Hydrostamm (Hydrometer), with ballast of mercury, for 

 liquids lighter than water. 



Hydrostamm (Hydrometer), with ballast of shots, for 

 liquids heavier than water. 



Hydrostamn (Hydrometer), with a small metallic balance, 

 the first idea of Nicholson's areometer. 



Photograph of the Hydrostamm (Hydrometer), enclosing 

 a thermometer. 



Mostra Umidaria (Hygrometer). An invention of Folli 

 da Poppi, perfected by the A ccadewia del Cimento ; the hygro- 

 scopical body is a band of paper. 



Hygrometer, at condensation, invented by the Grand Duke 

 Ferdinand II. dei Medici. 



Ball of Metal, filled with water, and prepared by the Accade- 

 mia del Cimento to serve in the experiments for the compression 

 of water. 



Ball of Metal, still containing some water that served for the 

 experiments of the Accademia del Cimento on the compression 

 of water. 



Natural Magnet, armed by the Accademia del Cimento. 



VARIOUS INSTRUMENTS. 



Two Tubes of Torricelli, one of which ends in a sphere. 

 They served him for his experiments on atmospherical pressure 

 in 1644. 



Telescope of Torricelli, with an object-glass of 50mm. 

 in diameter ; eye-glass, plano-convex, 22mm. in diameter. 



Day Telescope of Divini, from S. Severino. The diameter 

 of the object-glass is 70mm. ; the diameter of the first eye-glass 

 and of the second lens, double-convex, 33mm. The third lens is 

 wanting. 



Day Telescope of Ippolito Mariani, a Florentine, sur- 

 named il Tordo ; first practical optician; taught by Galileo. 

 Object-glass, 103 mm. in diameter. The eye-glass is composed of 

 two lenses, plano-convex, of mm. 48 in diameter. The second and 

 third lenses are similar to the eye-glass. 



