PKOCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 387 



increase of heat, while in some the combination is so slow that no percept- 

 ible heat can be produced by it. Another case is when these oils or fats 

 absorb oxj'gen, and if the oils are under pressure there is an increase of 

 heat ; but what accelerates it most is the sprpading of the oil over surfaces 

 of fibrous substances. All these cases present the oil in such thin layers 

 that it takes up large quantities of the oxygen of the air, and if there is 

 an increase of heat it will arrive at that point where it will take fire, that 

 is, the oxygen will rapidly unite with the carbon, or burn. We find cases 

 of this kind in the books ; an interesting article on this subject in Silliman^s 

 Journal, enumerates several, which the Secretary will now read. 



Mr. Chambers here read extracts from Sillimati's Journal on Spontaneous 

 Combustion. 



The Chairman. — This is ceriainly a very interesting question, for if in one 

 week a vast amount of property has been destroyed, we can safely say 

 that altogether, many millions have been consumed from this same cause. 

 The subject is also of great importance to insurance companies. Their 

 losses from this cause every year must be immense, and as there is no 

 record of a complete series of experiments to show at what points of heat 

 this combustion takes place, I think it is the duty as well as the interest 

 of the insurance companies to have a thorough scientific investigation 

 made into this matter. The expenditure of five thousand dollars in the 

 employment of competent chemists to experiment with articles liable to 

 spontaneous combustion, would well repay these companies. It is a sub- 

 ject to which the laws of science should be applied, and one in which we 

 are all more or less interested. 



Mr. Benjamin Garve^'. — It seems to me, Mr. Chairman, so little is known 

 on this subject that is definite, that all our theories are based upon mere 

 conjecture. The theories no doubt are very plausible, we know that no 

 chemical action takes place without oxj'^gen, and that all the combustion 

 which takes place in the air are acts of combinations of the elements of 

 the combustible body with oxygen. But there are other causes to be taken 

 into consideration, which might produce the same result. We know that 

 electricity follows a law very similar, and we may, with the same pro- 

 priety, ascribe many of the phenomena which take place as due to this 

 cause. Our knowledge, however, on this subject, is very limited, and I 

 mention these ideas in order to direct inquiry to this branch of chemisty. 



A specimen of paper made from the poplar wood was presented by Dr. 

 Parmelee, 



Manufacture of Sugar. 



The subject of the meeting — the manufacture of sugar in the North, was 

 announced by the Chairman. 



Dr. Dubois D. Parmelee read the following paper on the subject : 



We may understand by Sugar, those substances which are susceptible of 

 the vinous fermentation, that is, those which, by a peculiar decomposition, 

 are resolved into alcohol and carbonic acid. These are cane sugar, grape 

 sugar (sugar of starch, of honey, diabetic sugar), sugar of milk, and un- 

 crystalizable sugar. 



The " sugar of mushrooms" has been found to be mannite, which is not 

 fermentable. 



