ON THE DEVELOPMENT OF LIGHT FROM COAL-GA?. 



121 



the bottom what is called a " pauier," constructed of porcelain, and pierced 

 with numerous holes for the admission of air. The funnel is 8 X If 

 inches. With 26 candle gas it burned 2-5 cubic feet, and gave a light of 

 10 - 8 candles, or for 5 feet per hour 2L6 candles. 



Sugg has constructed a series of " London Argands," burning from 

 3 to 12 cubic feet per hour of common gas, and from 1-| to 7^ cubic feet of 

 cannel-gas per hour. Those from A to I resemble in every respect the 

 standard London burner already described ; K has, in addition, a single 

 or rat-tail jet in the centre, and that marked double is formed of two 



It is only right to state that all these burners are constructed to burn 

 common rather than cannel gas. A Silber Argand of 24 holes, with 

 chimney 8 X If inches, was tested at the same time for comparison, and 

 gave, for a consumption of 3*75 cubic feet per hour, calculated to 5 cubic 

 feet, an illuminating power of 2402 candles, a somewhat higher result than 

 was obtained with any of Sugg's series, and proving that Silber's Argand 

 is well adapted for burning cannel-gas. 



The standard of comparison is a sperm candle burning at the rate of 

 120 grains per hour, and in practice two candles are used. It is well known 

 to gas examiners that the candle cannot be depended upon to give a con- 

 stant illumination, so that a series of tests, using candles as the standard 

 of comparison, would be certain to present such ^regularities as to be of 

 little value. It would be out of place in this report to refer to the 

 methods proposed by Crookes, Harcourt, and others, for obviating this 

 difficulty by substituting other sources of light ; it is sufficient to indicate 

 the system pursued in making the tests with cannel-gas, the results of 

 which have been given. A 100-inch photometer was fitted up with two 

 complete sets of apparatus — each side having its experimental meter, 

 balance, governor, and pressure-gauge. At the right-hand side was the 

 light to be tested, and at the left two small straight or rat- tail jets, occupying 

 the exact position of the candles in the ordinary system of gas testing. 

 These were attached to a bracket hinged so that by the aid of two plumb- 

 lines they could be brought into exact position when required. The 

 Keate's candle balance, which was used for standardising the small gas 

 flames, was removed after a very careful test was made with the candles, 



