708 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



one by one. They should be washed in order to see whether the 

 grains have been artificially colored or not, and then dried in a 

 towel. The operation of roasting should be performed with great 

 care, and not cease until the grains have lost their horny texture 

 and admit of being crushed between the fingers. Catfcine, the 

 active principle of the berry, would be decomposed if the roasting 

 process were not conducted slowly, and stopped on attaining a 

 light brown hue. A dark brown color, or worse still a black, 

 would show that the berry had lost all its virtues. In order to 

 prevent the air from acting injuriously on the cofl'ec after roasting, 

 sugar should be sprinkled over it in the proportion of fifteen 

 grammes to every pound, and the whole should be well stirred. 

 In this way an impenetrable coating of caramel protects each 

 grain. After roasting the berries should be placed on iron plates 

 and left to cool in a dry place. No more cofiee should be roasted 

 at a time than is required for the day. The roasting should not 

 be done in a closed cylinder, as is the common practice, Init in a 

 frying pan, so as to be able to watch the various changes of color. 



Graphite. 

 This form of carbon commonly called black lead or plumbago 

 occurs, mechanically mixed with a small proportion of iron, in 

 granite, gneiss, mica-slate, primitive limestone and greenstone. Its 

 principal use in the arts is in the manufacture of pencils and cruci- 

 bles. It is found in many places in this country, but is seldom of 

 the first quality. The' best graphite in our market is brought 

 from Ceylon. Graphite can be formed artificially by subjecting 

 iron, in contact with carbonaceous matter, to a very high tempera- 

 ture. It may separate in the crucible in which the experiment is 

 made or may penetrate the iron itself. By treating gray cast-iron 

 with hydro-chloric acid and other re-agents carbon is separated in 

 crystalized six-sided tables In iron furnaces graphite is artificially 

 formed on. a large scale. Professor Playfjiir, before the British 

 Association, recently spoke of a furnace at the Alfreton Iron 

 Works, which was forty or fifty years old, or about ten times the 

 average age of a furnace. It was recently repaired, and he had 

 then opportunity of ascertaining why it lasted so long. He found 

 it lined with graphite three or four inches thick, not by the manu- 

 facturer but by the operations of nature. The carbon in the iron 

 had been squeezed out, and the whole furnace was probably lined 

 with graphite. 



