74 HEPORT-^1872. 



quantity of the oiled cottou that just filled a common lucifer-match box was tried; 

 ^vithin au hour it was on fire, the temperature of the chamber being 1G6° Fahr. 



Maw Linseed-oil, as generally supposed, does not so readily set tire to cotton as 

 the boiled oil ; but in two experiments, where the size of the box employed was 65 

 in. long by 4^ in. square in tlie ends, active combustion was going on in the one 

 ease in five and the other in four hours. 



JRape-oil put up as in first experiment on boiled linseed resulted, in two trials, in 

 the box and cotton being found in ashes within ten hours. The box being put up 

 at night, the result was only observed in the morning. In one trial the cotton did 

 not ignite in six hours. The chamber in the cases of this oil and raw linseed was 

 kept about 170° Fahr. ; with the five following oils at a little over 180° Fahr. The 

 quantity of waste used was loosely packed in a paper box, holding about the six- 

 teenth of a cubic foot. 



Gallipoli OUce-oil. — The two trials made with this oil gave closely similar results ; 

 in one case rapid combustion was going on in a little more than five, and in the 

 other within six hours. 



Castor-oil. — The oxidation of this oil proceeds so slowly that only on the second 

 day the interior of the box was found to be a mass of charred cotton. Its spec, 

 grav. (963) is remarkably high, and its chemical nature very distinct from the 

 other vegetable oils tried, which no doubt has some intimate connexion with its 

 slow oxidation. 



Three oils of animal origin were tried with eifeets very distinct and insti-uctive. 



Lard-oil, an oil of an ordinary specific gravity, viz. 916, produces rapid com- 

 bustion in four hours. 



Sj)erm-oil, which has a specific gravity of only 882, and is not a glyceride, 

 showed its unusual chemical character by refusing to char the waste. 



Seal-oil, which has a strong fish-oil odour, not unlike the sperm, but a specific 

 gravity of 928, produced rapid ignition in 100 minutes. 



Comparing raw linseed with lard- and seal-oils, it would appear that the state- 

 ment is not altogether correct, that drying oils are more liable to spontaneous 

 combustion than non-drying oils. The author has also some reason to believe that 

 the rate at which oxidation takes place does not chiefly depend on the presence of 

 small quantities of ozotized or other easily putrefiable matters, but rather on the 

 particular olein. However, further inquiry on this point is necessary. 



The author made at least two experiments with each oil, and got remark- 

 ably uniform results. The ignition of the cotton can be calculated on for any oils 

 with about the same certainty as the point at which sulphur or other combustible 

 material takes fire when heated in the air; so that the term spontaneous combus- 

 tion may be objected to, for the same reason that Gerhardt objects to spontaneous 

 decomposition produced by oxidation. 



The heavy oils from coal and shale being chiefly the higher olefines, have a 

 remarkable efi'ect in preventing this oxidation, undoubtedly by giving a certain 

 protection from the air. Mixtures of these oils with 20 per cent, rape, gave no 

 indication of heating whatever at 170° Fahr. ; and even seal-oil, with its own bulk 

 of mineral oil added to it, did not at 135° reach a temperature sufficient to char 

 the cotton. 



The author hopes that these remarks will lead to a more elaborate inquiry into 

 this subject, both for scientific and practical purposes. 



On the Bust tlirown up hy Vesuvius darinr/ the late Eruption. 

 Bj George Glabstoxe, F.C.S. 



During the eruption which took place this spring a large quantity of fine powder 

 which had been ejected by Vesuvius filled the atmosphere, and was deposited OA'er 

 the surface of the country around. Some which fell at Oasa Miceiola, in the 

 Island of Ischia, at 25 miles in a direct line from the volcano, was collected and 

 subjected to examination. It proved to co^si^t entirely of silica and the magnetic 

 oxide of iron. The microscope showed that the grains were very uniform in size, 

 and consisted of an aggregation of quartz crystals dotted over with still more 



