TRANSACTIONS OP THE SECTIONS. 579 



splint coal required in 1833, to make a ton of cast iron, was 

 only one third of what was used in 1829. The blast machinery 

 continued the same, but the same blast made twice as much 

 iron as in 1829. 



The same coal produced thrice as much cast iron; the same 

 blast twice as much. 



The iron-furnaces alluded to are worked 23 hours out of 

 the 24; a half-hour every evening, and another every morning, 

 being occupied with letting off the iron produced. 



During every working-hour, the solid materials which feed 

 the furnace at the top amount to 2 tons almost exactly, while 

 the air forced in at the bottom, in the same time, amounts to 

 the surprising quantity of 6 tons. 



Since a smelting-furnace must have a certain elevated tem- 

 perature, in order to work it favourably, when we consider 

 the cooling effect of 6 tons of air an hour,— 2 cwt. a minute, 

 — supplied at the bottom of the furnace, and entering near the 

 hottest part, it is easy to account for the increased energy of 

 the furnace when this prodigious refrigeratory is removed, by 

 heating the air before it passes into the furnace. 



On hydrated Salts and metallic Peroxides ; with Observations 

 on the doctrine of Isomerism, By Professor Graham. 



Various classes of salts, besides the arseniates and phos- 

 phates, contain water, which is essential to their constitution: of 

 this the sulphates of magnesia, and the protoxides of zinc, 

 manganese, iron, nickel, copper, and cobalt, are examples. 



These salts crystallize from their aqueous solutions, either 

 with seven or five atoms of water, one of which is in a state of 

 much more intimate union than the other six or four. Thus, 

 crystallized sulphate of zinc loses six atoms of water, at a tem- 

 perature not exceeding Q5°, when placed over sulphuric acid 

 in vacuo, but retains one atom of water at 410° and all inferior 

 temperatures. This salt may be viewed as a sulphate of oxide 

 of zinc and water, with six atoms of water of crystallization; a 



constitution which may be expressed as follows, HZnS-t-6H. 

 This sulphate may be made anhydrous, but when moistened 

 always regains one atom of water, slaking with the evolution 

 of heat. This last atom of water appears to discharge a basic 

 function in the constitution of the salt, and affords a clue to the 

 disposition of this sulphate to form double sulphates. Sulphate 

 of zinc combines with sulphate of potash, and forms a well- 

 known double salt, in which the basic water of the sulphate of 



2 p 2 



