V. THEKMOMETRIC. 941 



3744. Two Self-acting Filtering Glasses, for micro- 

 scopical reagents. Prof. Jessen, Eldena> in Pomerania. 



V. THERMOMETRIC APPARATUS USED IN 

 PHYSIOLOGICAL RESEARCH. 



Thermometer, in the shape of a little frog; it contains 

 balls of different densities and differently coloured, which sink 

 in succession as the fluid within the instrument rises in tem- 

 perature and consequently diminishes in density. It served, being 

 tied to the arm, to determine the degrees of heat in fever. 



The Accademia del Cimento* 



The thermometer invented by Galileo underwent afterwards important 

 improvements. Giov. Francesco Sagredo, a noble Venetian, and a very 

 great friend of Galileo, wrote to him on the 9th of May 1613 as follows : 

 *' I have succeeded in reducing the instrument, which you have invented for 

 " measuring heat, into several very convenient and delicate shapes, inasmuch 

 " as the difference between the temperature of two rooms can be seen up to 

 " 100 degrees, &c." 



It was Sagredo, who, in 1615, first hermetically closed the thermometer. 



Other improvements were effected by the Grand Duke Ferdinand II. The 

 following is what Padre Urbano Daviso says about them in his book entitled 

 " Pratiche Astronomiche." Having first of all described a thermometer similar 

 to Galileo's, he proceeds " But His Serene Highness, not being satisfied with 

 " this invention, endeavoured to render it absolutely perfect. He constructed 

 " a little glass phial, of about the size of a musket-ball, with a neck of about 

 " the length of half a palmo, but so thin that it is barely possible to insert a 

 *' millet-seed into it. Being filled with well refined spirit, either coloured 

 " or in a natural state, in sufficient quantity for it to reach up to the middle 

 " of the tube, and then the mouth being closed with a seal of hermete, it will 

 " show by means of the rising or falling of the liquid in the neck (which 

 " must have points marked on it for that purpose) the degree of greater or 

 " less heat or cold* And it has this advantage over the other instrument, 

 " namely, that the latter could only show the state of the air, whilst this one 

 " indicates, in addition to the temperature of the air, that of any liquid 

 " in which the bulb shall have been immersed ; hence it will be possible 

 " to warm water, or a room, or a furnace to any degree, and to keep it 

 " in that state, or increase it, just as one pleases. Thus it will be easy to 

 " find out when a thing has been heated to the degree that was necessary for 

 " cooking it properly, operations from which, it may be said, that the 

 " chemical art has received its finishing touch. And in the same way it will 

 " be possible with instruments of this kind to find out the state of heat or 



" cold of any place or province And by this means it has been 



" discovered that the water of wells and springs, as also cellars, grottoes, 

 " and other deep subterranean places, which in winter seem to our senses to 

 " be warmer than in summer, are, in fact, of the same temperature at both 

 " seasons. And we are, therefore, forced to say that the apparent difference 

 " comes from the surrounding atmosphere which affects our senses, and not 

 " from any change in the degree of heat or cold in the vaults." 



As to the way of dividing them into degrees, the Diario dell' Accademia 

 del Cimento says that the cinquantigrado " immersed in melting snow, 



