105 



of a cork sen -^ , We then have the haok proof. By 

 boiling a little more, the thread no longer break? or 

 in breaking, it remains unscrewed and does not 

 twist like a cork screw ; we then have reached the 

 desired state and have the thread proof. 



With the hook proof the mass still contains 10 

 per cent of water ; with the thread proof it contains 

 only 5 per cent. 



This is called evaporation and boiling a air libr', 

 in opposition to the corresponding operations that I 

 have already described, and which are called evapo- 

 ration and boiling in vcwuo. 



Experiments on a small xcalt. 



Those who wish to experiment on a sn.aii scata, 

 should use this method, which is always the basis 

 of the manufacture. 



To extract the juice a screw or lever press is used. 

 The same copper boiler would be used for defeca- 

 tion, evaporation and boiling down. As steam 

 would not bf> at hand, a moderate open fire could be 

 used so as not to burn the syrup. 



In this case the turbine can not be employed, 

 conical moulds like the sugar loaves of commerce 

 are used, or rather boxes deeper than broad, having 

 a spout on a level with the bottom. The moulds have 

 also a hole at the pointed extremity. These openings 

 being closed UD, the boiled syrup is emptied into the 

 vessels and they are allowed slowly to crystallize in 

 a place heated to 8C. To obtain large crystals of 

 6 



