INDEX. 527 
Woop, Mr. Kinder, his observations on the local preva- 
lence of idiotism, and its connection with goitre, 83. 
EE 
Note on Oil and Coal Gases. 
Page 78. ‘Oil gas is better, volume for volume, than 
coal gas, by about 10 per cent.” 
This is supposing the value proportional to the oxygen 
required for their combustion, and that good average coal 
and oil gases require for every 100 about 170 and 190 
oxygen respectively, as would result from Dr. Henry’s 
experiments. I find the average of coal gas from the 
Manchester gas works requires very nearly 170 per cent. 
of oxygen; but the oil gas from Mr. Hoyle’s works now 
(1824) usually requires about 225 oxygen. ‘This brings the 
ratio of coal and oil gases, as 3 to 4. 
From a recent train of experiments however I find that 
the Aeat from the combustion of these gases is accurately 
or very nearly in proportion to the oxygen consumed, and 
that whether the gases are diluted or not: but the light 
1s nearly in the compound ratio of the oxygen consumed 
and the density of the combustible gas, when this last is 
nearly pure ; but if itis diluted with any incombustible 
gas or even with hydrogen, the diminution of light is 
vastly greater than in propertion to the dilution. I find 
one eubic foot of oil gas (sp. gr. 0.9 +) equivalent to 2 or 
2+ of coal gas, (sp. gr. 0.6 +) for the purpose of illumina- 
tion. 
) 3. D. 
July, 1824. 
Printed by the Executors of S. Russell, Manchester, 
