204 THE LIFE OF A BIRD. 



ing a part of the glaze in cards, and paper of some 

 kinds. But its more characteristic property is that 

 of coagulability. With this phenomenon every 

 one who is acquainted with the every day opera- 

 tion of the boiling of eggs is already familiar. The 

 egg, when placed in the boiling water, has entirely 

 fluid, though viscid contents. After an expo- 

 sure of a few minutes to water of this high tem- 

 perature it may be taken out a solid mass; the 

 shell may be stripped from it, and the once fluid 

 interior is now converted into a dense substance, 

 which will bear to be tossed about like a ball, and 

 is often in fact so employed, without its integrity 

 being broken. When it is remembered that 

 nothing in the shape of a chemical ingredient has 

 been added to it, and this remarkable change is 

 solely due to the influence of heat, and that not 

 of a higher degree than 212, coagulation in fact 

 taking place at a little above 160, this pheno- 

 menon must be considered as one of great singu- 

 larity and interest, and not the less so that it 

 occurs a thousand times under our domestic obser- 

 vation. The addition of several chemical sub- 

 stances will produce the same effect. It is on 

 this account very usefully employed in cases of 



