232 Dr Fyfe on the Illuminating Power of Coal-Gas, §c. 
In conducting experiments with the view of ascertaining 
the illuminating power of oil, compared with that of gas, I 
used argand oil-lamps of the common construction, and also 
others with contrivances adapted to them, which have been 
lately recommended for increasing the light. The first trials 
were made with sperm oil, the cost of which, at the time the 
trials were made, was 9s. 8d. per gallon, that is, 1s. 23d. per 
pint. It was burned in a common argand, consuming the oil 
under the most favourable circumstances. In endeavouring 
to fix the illuminating power, I contrasted it with an argand 
gas burner, having forty-two holes, and consuming three feet 
per hour. I found, however, considerable difficulty in coming 
to accurate results, partly from the variation in the flame of 
the oil, partly also from the difference in the appearance of 
the shadow. Six trials were made at different times, and with 
the lights at different distances. These varied from 2 to 2.4, 
taking the oil as 1. The average of the different trials gave 
2:35. <A pint of oil was found to burn 14 hours, at a cost of 
143d. ; the consumpt of gas for the same time (3 x 14) was 42 
feet, at an expense of 41d., but the light was as 2.25 to 1. 
The comparative expense, therefore, light for light, would be 
as 143d. x 2.25 to 44d.; that is, as 8 to 1, or very nearly so. 
Rectified whale oil was next tried, the cost of which was 
4s. 8d. per gallon. A pint, when consumed under the most 
favourable circumstances, was found to burn 12 hours; and 
contrasted with the gas argand as before, the light was as 1 to 
2.54. The cost of oil was 7d., that of gas for the same time 
was 32d., but the light was as 1 to 2.54; the expense was, there- 
fore, for the same light, as 7d. x 2.54 to 33d.; that is, 5 to 1. 
In the preceding trials the oil was consumed in a com- 
mon argand, due attention being paid to the different circum- 
stances affecting the consumpt, such as the kind of wick, the 
height of flame, &c. The next trial was made with the lamp 
lately introduced under the name of solar lamp. In this a 
cylinder surrounds that containing the wick, with the upper 
part bent inwards, so that the aperture being contracted, the 
current of air that passes up between the one cylinder and the 
other, striking against the horizontal part of the outer one, 
causes a contraction and lengthening of the flame; a longer 
