233 
active competition. Mechanical improvements, however, 
remained his favourite study, and he kept himself acquainted 
with whatever steps of progress were made during a long 
and useful life. At the time of his death, on the 30th 
October, 1855, he was the oldest member of the Society. 
To its Memoirs he contributed four valuable papers, — “ On 
the Rise and Progress of the Cotton Trade” (1815), “ On 
the Poor Laws” (1819), “On the Influence of Machinery 
on the Working Classes” (1826), and “A Memoir of 
Crompton.” In these he has displayed consummate judg- 
ment and great knowledge of his subjects, although it must 
be allowed that since his time, his views on the commercial 
relations and foreign policy of this country have been greatly 
modified. 
Dr. J. P. Joule read a Paper, “ On the Efflux of Air.” 
The Author, after referring to the experiments and views of 
Newton, Bernoulli, Venturi, Savart, and others, on the flow 
of liquids and elastic fluids, described some experiments he 
had recently made on the flow of air through orifices in thin 
plates, and through tubes. The pressures employed were 
from 5'6 inches to 1*44 inches of water. The quantity of air 
discharged was found to observe the well-known law of the 
square root of the pressure. The Author’s experiments on 
the velocity of air discharged through orifices of different forms 
were made with a pressure of 1*44 inches. For very small 
pressures V=v/2^A; calling this unity the velocity through 
holes in thin plates, is 0’607 ; through pipes of diameter 
equal to their length, 0’767 ; and through pipes of diameter 
equal to their length, furnished with a piece of wider tube for 
the entrance of the air, 0‘893. 
Dr. Joule also gave results of the boiler testing, by expan- 
sion of water, described by him at a previous Meeting, the 
temperatures employed were between 97° and 126°, and the 
testing pressure 65 lbs. on the S({uare inch. 
