104 Transactions of the 



Petroleum generally occurs in depressions of the strata, and is 

 brought to the surface by means of artificial Avells, which, in America, 

 costs about £1200 a well. When the oil is reached it generally rushes 

 up with great force, aud in vast quantities, sometimes as much as 

 1000 barrels a day being ejected ; but the quantity very soon dimin- 

 ishes, and the miners have to resort to pimips. Besides the artificial 

 wells there are such things as intermittent wells, which only produce 

 oil two or three times a day, but when the oil is ejected it very often 

 rises to a height of fifty feet. 



All petroleum contains a greater or less amount of bitumen or 

 asphaltum, and also a certain amount of paraffin. This paraffin is 

 separated from petroleum by cooling mixtures and pressure. The 

 average yield is about one pound of paraffin for four gallons of petroleum. 

 The paraffin is used for lubricating and for candles. The more bitu- 

 men there is in petroleum, the more like tar does it become ; and if 

 the amount be very great, the petroleum passes into a substance which 

 possesses so little fluidity as to be sohd at ordinary temperatures. In 

 this condition it is found in Tar Lake, in the Island of Trinidad, and 

 is then used for making pavements. 



The want of a suitable vessel for the transportation of petroleum 

 has long been felt. Near the Burmese springs vessels pecuharly 

 suitable for the exportation of petroleiun are manufactured. Ordinary 

 barrels, although tight enough to prevent other hquids from passing 

 through them, do not prevent the leakage of petroleum. It is said 

 that ten per cent, of petroleum is lost on the journey from the wells 

 in Pennsylvania to New York. When petroleum was first exported 

 from America to Europe in ordinary casks, the casks were found empty 

 on arriving. At present barrels lined with zinc are used to transport 

 petroleum beyond sea. 



The uses of petroleum are various. When rectified it is used as an 

 illuminator, and it gives a much brighter light than either oil or 

 paraffin candles, and besides, it has this advantage over oil, that it does 

 not dirty lamps like olive oil. It has also been proposed to use 

 petroleum as a producer of motive force, and a machine has been 

 constructed in which petn)leum is used as fuel. The thicker kinds of 

 petroleum are used for lubricating machinery. Pecroleuiu is also used 

 for dissolving grease. The paratfiuand bitumen contained in petroleum 

 are also made use of as already mentioned. 



Of the origin of peti'oleum very little is known, but the similarity 

 existing between petroleum and the compounds produced by the 

 destructive distillation of coal, renders it probaljle that peti'oleum has 

 been formed by the destruetiv'e distillation of animal and vegetable 

 matter. The general opinion as to the origin of petroleum is, that it 

 has been produced by the action of heat on coal beds. But to this 

 theory there a'-e several objections; thus, fur instance, anthracite, which 

 would be the most likely of all kinds of coal to be the residue of a 

 process of destructive distillation, as it contains the smallest amount 

 of volatile substances, does not shew any indications of having been 

 exposed to a temperature high enough to volatilise petroleum. 



