ESTIMATION OF TANNIN IN SOME BARKS FROM BRITISH GUIANA. 367 



cheaply than the oil can be extracted from coal by the agency of heat, coal- 

 oil manufacturers will have eventually to give over the field to the rock-oil, 



We give a brief description of the oil-wells : — These are borings 

 through the solid rock from 8 to 6 inches in diameter, and of various 

 depths, from 50 to 500 feet, the drill being kept in operation till a vein 

 of oil is " struck,"' or the attempt abandoned. If successful, the hole 

 is tubed, and a pump, worked by hand or the feet, or steam, put in opera- 

 tion, and rude tanks erected to contain and separate the oil and water 

 which flow from the pump. The weils in successful operation number 

 about 200, principally in Pennsylvania, Virginia, and Ohio ; and the total 

 number in operation and in course of construction at the present time is 

 about 2,500. The average cost of boring and fitting up is about $ 1,200, 

 and the average production of oil from the successfid wells is about 8 

 barrels, or 320 gallons, per day each. 



It appears that within the past year (1860), over half a million of 

 dollars have been expended at Pittsburg for steam-engines, boilers, tubing, 

 &c, for the oil district : 17,000 barrels of crude oil have been received, and 

 $ 219,500 worth of purified oil disposed of ; $ 176,976 were received for 

 steam-engines and boilers, and $ 178,002 for tubing and drills. The cost of 

 an engine has averaged less than $ 300, but never above that sum. The 

 amount of oil sold during the year, 8,700 barrels. Amount realised, at 

 $ 25 per barrel, $ 219,506. Total cost of steam-engines, boilers, machi- 

 nery, tools, ropes, &c, purchased here for oil operations during the last 

 twelve months, $ 527,720. Value of refined oil sold by the refiners, 

 $ 219,500. Value of oil received by railway and river, $ 203,208. This is 

 exclusive of business done in Pittsburg in coal-oil. 



ESTIMATION OF TANNIN IN SOME BARKS FROM BRITISH 



GUIANA. 



BY JOHN MULLIGAN, 

 Student in the Evening Class for Practical Chemistry, Museum of Irish Industry. 



As Mr Fry, in his valuable "Notes on Tanning Substances," which 

 appeared in the May number of the Technologist, at p. 299, has alluded 

 to the barks of British Guiana, perhaps the following determination of 

 tannin in some barks from that colony may be of interest, and form a kind 

 of supplement to Mr Fry's paper. The quantity of tannin in the barks 

 was estimated for the purpose of ascertaining whether these barks could be 

 profitably used as tanning materials. The method employed in determin- 

 ing the quantity of tannin in the barks was similar to that used by Mr 

 Dowling and myself on a former occasion.* 



* Estimation of Tannin in some Tanning Materials, by Messrs Mulligan and 

 Dowling. Vide ' Chemical Gazette/ Nov. 15, 1859. 



