ON PETROLEUM AND PHOTOGEN. 'it 



Whatever may be the precise nature of the Boghead coal, it is a most 

 valuable producer of oils. One ton yields 120 gallons of crude oil, of 

 which 65 gallous are lamp-oil, 7 paraffin oil, and 12 lbs. of pure paraffin 

 can be extracted. 



Ill, Bitumens. — Deposits of this substance exist in various parts of 

 the world, and have been lately employed largely in that branch of 

 manufacture which we are now considering. The largest deposit known 

 is the celebrated Pitch-lake of Trinidad, three miles in circumference. 

 The bitumen is solid, and cold near the shores, but gradually increases 

 in temperature and softness towards the centre, Avhere it is boiling. The 

 solidified bitumen appears as if it had cooled in large bubbles as the 

 surface boiled. The ascent to the lake from the sea, a distance of three- 

 quarters of a mile, is covered with hardened pitch, on which trees and 

 vegetables flourish, and contains small pools of water, clear and trans- 

 parent. The lake is underlaid by a bed of coal. Mr. S. P. Wall shows 

 that the asphalt of Trinidad and Venezuela belongs to strata of tertiary 

 formation (the upper miocene or lower pliocene age), which consists of 

 limestones, sandstones, and shales, associated with beds of lignite. The 

 bitumen 13 found not only in the pitch-lake, but in situ, where it is 

 confined to particular strata, which were originally shales containing 

 vegetable remains. These have, he says, undergone " a special mine- 

 ralisation, producing a bituminous matter instead of coal or lignite. 

 This operation is not attributable to heat, nor of the nature of a dis- 

 tillation, but is due to chemical reactions at the ordinary temperature 

 and under the normal conditions of climate." — (Proc. Geol. So:, of 

 London, May, 1860.) 



One ton of the Trinidad bitumen yields 42 gallons of oil fit for 

 lamps, and 11 for the purpose of lubrication. The bitumen contains 

 sulphur. Sulphuretted hydrogen issues from the pit where the mineral 

 is discharged from the earth. The first distillate is full of impurity, 

 such as pyroxylic spirit and other products of the distillation of wood, 

 which give evidence of the vegetable origin of this pitch ; it is also 

 accompanied by a peculiar volatile oil, which imparts to it a most un- 

 pleasant odour and renders it difficult to purify. 



From time immemorial the burning and naphtha springs of Persia 

 and other parts of the East have been known. But these substances 

 were not utilised in England, until an agent of Price's Candle Company, 

 in his search after new sources of palm oil, discovered a material fitted 

 for his purpose in the so-called mineral tar of Rangoon, in the Birman 

 Empire. Iron tanks were constructed, and were filled with the crude 

 tar at the wells. This, when refined at the Sherwood works, yielded 

 solid paraffin, heavy lubricating oil, Belmontine oil, &c. The tar is ob- 

 tained by sinking wells in the soil of blue clay, about 60 feet deep ; 

 the fluid oozes in from the soil, and is removed ; it is of the consistence 

 of goose-grease, of a green-brown colour, and of a peculiar bat not dis- 

 agreeable odour, and contains only 4 per cent, of solid matter. It is- 

 said that there are now 520 wells, which yield 400,000 hogsheads 



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