278 MORTAR. 



vegetables combines with oxygen of the 

 air, and forms carbonic acid gas. Putre- 

 faction, therefore, is only another species 

 of combustion. 



Q. What changes do ANIMAL bodies undergo 



from PUTREFACTION ? 



A. The same as vegetables, with this 

 addition they give out ammonia, 

 sulphur, and phosphorus also; which 



causes the offensive smell of putrefying 



i u j- 

 animal bodies. 



Q. Why is LIME heated by a KILN ? 



A. All marl and chalk abound in 

 carbonic acid; and (when heated by a 

 fire) the carbonic acid flies off in gas, 

 producing great heat. 



Q . What is MORTAR ? 



A. Lime mixed with sand and water. 



Q. What is LIME ? 



A. Lime-stone burnt produces lime. 



Q. Why is the lime-stone BURNT, in order to 

 make it into LIME ? 



A. The fire expels the carbonic acid, 

 and converts the hard lime-stone into a 

 loose powder. 



Q. Why does MORTAR become HARD, after a 

 few days ? 



