PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 345 



leaf is pressed into the lead, forming- a mold for an electrotype plate, which 

 is employed for printing. Inks of the proper color are used in the printing, 

 and where several colors are required they are worked on the same plate, 

 so as to print the whole at one impression. The Consul-General of Austria, 

 Charles F. Loosey, presented several magnificent volumes of these prints 

 to the American Institute a few years ago. It was a most valuable and 

 acceptable donation, and I trust was properly recognized and appreciated. 



A volume of the prints was brought from the library, and greatly admired 

 by those present. 



The subject of "Illuminating Materials" was selected for the next meet- 

 ing, and the society adjourned. 



Thomas D. Stktson, Secretary. • 



American Institute Polytechnic Association 



3Iay 29, 1862 

 The Chairman, Prof. Chas. A. Joy, presiding. 

 The Chairman announced the regular subject of the evening to be 



ON, I 



Illuminating Materials, 



and, as he proposed the subject, he proceeded to open the discussion. 



Illuminating materials are found in all three forms of matter; solid, 

 liquid and gaseous. They generally contain hydrogen and carbon, and tlie 

 light is emitted by the carbon while it is in an incandescent state, after it 

 is heated by the burning of the hydrogen, and before it is itself consumed. 

 I have in my hand a list of some 16 or 18 materials which have been used 

 for producing light. 



One of these is tallow. This has been used from time immemorial. Some 

 of the vegetable oils liave also been used from the most ancient times of 

 which we have any knowledge; among these are palm oil and olive oil. 



In Greece, 2,000 years ago, they used lamps essentially the same as those 

 which are used in some countries at the present day. I hold in my hand an 

 earthen lamp that was dug from the ruins of Athens. It has a handle upon 

 this side and this is the place for the wick. The material burned in it was 

 probably olive oil. It differs, you see, but very little from the lamps which 

 we use, and all over Germany the workmen use lamps precisely like this, 

 only their lamps are made of tin. ^ 



Dr. Stevens. — Earthen lamps are used extensively in the western part of 

 this country. 



The Chairman.— The kind of fat, either animal or vegetable, used for 

 illuminating in any country, is determined by the supply; it is a mere 

 question of economy. 



Besides the hydrocarbon compounds, there is a class of substances of a 

 different character employed for the production of light. Among these are 

 lime in oxy hydrogen light; the carbon points for the electric light; mag- 

 nesium and quicksilver. 



