﻿146 Transactions. — Miscellaneous. 



Art. XIV. — On some Experiiments showing the Relative Value of Nev} South 



Wales and New Zeakmd Coals as Gas-producing Materials. 



By J. Rees George. 



[Read before the Wellington Philosophical Society, SOih September, 1871.] 



The table giving tlie result of tests of coal from various mines will be of 

 interest at the present time to those desirous of developing the various mineral 

 resources of ITew Zealand. I propose to add a few remarks showing the manner 

 in which the experiments were conducted, and such explanation as may be 

 necessary to show the relative value of the different samples tested. 



In testing coal for the purpose of ascertaining its value as a gas-producing 

 material, the result depends so much on the heat at which the retorts are 

 worked, that it is only by numerous trials, under variable conditions, that its 

 true value for practical purposes can be ascertained. Some coal will give a 

 good result when worked at a great heat, which, if worked at a low heat, 

 would prove the reverse of economical. The Old Lambton coal is an instance ; 

 this, at a high heat, gives a large qiiantity of gas, but with a small illuminating 

 power and at a moderate heat gives less gas, but of better quality. The 

 results given in the table were ascertained by comparing the illuminating 

 power of the gas burning in a standard Argand burner of fifteen holes, con- 

 suming nearly six cubic feet per hour, against a standard sperm candle, burning 

 120 to 125 grains per hour, the power being measured on the graduated scale 

 of a photometer as in use by the government examiners in London. The 

 pressure of gas, in cases where samples of 1 1 2 pounds weight were tested, was 

 2 "5 inches, or about the same pressure at which the gas is delivered to con- 

 sumei's from the mains ; in cases where samples of only seven pounds or ten 

 pounds were tiied, the pressure was 1 "4 inches, and this difference of pressure 

 accounts largely for the decreased power of illumination shown in the smaller 

 samples. In the case of the lai-ger samples the illuminating power was 

 ascertained immediately after the gas had passed through the purifiers, before 

 being stored, or subjected to the friction of a long length of pipe ; while in 

 the case of the smaller samples it could not be tried until some two or three 

 hours after storage, and passing through a length of, pei'haps, 100 feet or 

 more of a small tube. These circumstances combine to make the small 

 samples show a worse result than the larger quantities, as storage and friction 

 rapidly i-educe the illuminating power of coal gas. 



The mode usually adopted for ascertaining the exact standard illuminating 

 power of gas is by reducing the amovmt consumed by the gas burner and 

 candle respectively to a standard quantity of five cubic feet of gas, and 120 

 grains of sperm per hour. In the results given this calculation has not been 

 made, in consequence of the want of convenient apparatus for ascertaining 



