ON GASEOUS EXPLOSIONS. 179 
Hopkinson’s experiments on the compression of air in a gas-engine 
cylinder. 
Dr. Watson’s researches on the efficiency of a petrol motor are 
included in the report. Dr. Watson made a simultaneous measure- 
ment of the quantities of air and petrol taken into the engine and of 
the chemical composition of the exhaust gas. The point brought out 
was that the ratio of hydrogen to carbon in the exhaust gas was greater 
than the ratio of hydrogen to carbon in the petrol used. Additional 
evidence of this discrepancy is furnished by some experiments of 
Professor Hopkinson, and the experiments of Hopkinson and Watson 
are in agreement. 
The report concludes with an account of the experiments on radia- 
tion carried out by Professor Hopkinson. 
There are two appendices: one relating to Regnault’s corrections in 
connection with the determination of the specific heat of air, and the 
other relating to Deville’s experiments on the dissociation of gases by 
Dr. Harker. 
The third report is devoted mainly to the consideration of the 
subject of radiation from gases. A brief general history of the subject 
is given, together with a record of the experiments of Professor 
Hopkinson and of Professor Callendar. The report discusses the direct 
effect of radiation on the efficiency of internal-combustion motors, the 
amount of radiation from flames, and the molecular theory of radiation 
from gases as well as the question of the transparency of flames to 
their own radiation. There is an appendix on the radiation of flames 
by Professor Callendar, giving some account of experiments made with 
a Méker burner; a second appendix on the radiation in a gaseous 
explosion by Professor Hopkinson; and a third appendix which 
contains abstracts from various papers relating to the application of 
heat radiation from luminous flames to Siemens’ Regenerating 
Furnaces. 
The fourth report merely notes the number of meetings held during 
the year, and states that, partly owing to the breakdown of apparatus 
and partly to the demands made upon the time of the various investi- 
gators, only two notes were read; consequently it was decided that 
the work then on hand should be included in the report for the 
following year. 
The fifth report continues the discussion of the effect of radiation, 
and is devoted mainly to the consideration of the factors which deter- 
mine the heat flow from the gas to the walls of the cylinder. The 
remarkable effect of turbulence on the rate of combustion is first 
mentioned in this report. Particulars of Dr. Dugald Clerk’s experi- 
ments are given, and these experiments definitely establish the fact 
that but for turbulence the speed at which modern internal-combustion 
engines are run would be impossible. Professor Hopkinson’s experi- 
ments, in which a fan was placed inside a closed vessel and the rates 
of combustion observed with the fan at rest and in motion, are recorded 
in the report, and confirm Dr. Clerk’s results. 
In the sixth report the resignation of Dr. Dugald Clerk and 
Professor Hopkinson from the Joint Secretaryship of the Committee is 
N 2 
