144 NOVUM ORGANUM 



37. There are many degrees in the susceptibility of heat. 

 And, first, it must be observed how much a low gentle heat 

 changes and partially warms even the bodies least suscep 

 tible of it. For even the heat of the hand imparts a little 

 warmth to a ball of lead or other metal held a short time in 

 it; so easily is heat transmitted and excited, without any 

 apparent change in the body. 



38. Of all bodies that we are acquainted with, air admits 

 and loses heat the most readily, which is admirably seen in 

 weather-glasses, whose construction is as follows: Take a 

 glass with a hollow belly, and a thin and long neck; turn 

 it upside down, and place it with its mouth downward into 

 another glass vessel containing water: the end of the tube 

 touching the bottom of the vessel, and the tube itself lean 

 ing a little on the edge, so as to be fixed upright. In order 

 to do this more readily, let a little wax be applied to the 

 edge, not, however, so as to block up the orifice, lest, by 

 preventing the air from escaping, the motion, which we 

 shall presently speak of, and which is very gentle and deli 

 cate, should be impeded. 



Before the first glass be inserted in the other, its upper 

 part (the belly) should be warmed at the fire. Then upon 

 placing i fc as we have described, the air (which was dilated 

 by the heat), after a sufficient time has been allowed for it 

 to lose the additional temperature, will restore and contract 

 itself to the same dimensions as that of the external or com 

 mon atmosphere at the moment of immersion, and the water 

 will be attracted upward in the tube to a proportionate ex 

 tent. A long narrow slip of paper should be attached to 



more quickly only because the draught of air is more rapid, the cold dense 

 air pressing rapidly ; nto the heated room and toward the chimney. Ed. 



