TRANSACTIONS OF THE SECTIONS. 
113 
He also read an account of certain improvements on steam- 
engines, for making available the power of the steam of high-pressure 
boilers, which is below the pressure of the atmosphere, by allowing 
the high-pressure steam to pass off into the atmosphere, and allowing 
the steam of low pressure to pass into a condenser through a secon¬ 
dary slide. He gave a description of a method of securing the seams 
of boilers by longitudinal instead of the present circular clenches; 
and of a machine for drilling boiler-plates as rapidly as they can be 
punched by the punching-machine. 
Mr. Roberts exhibited a machine which renders objects visible 
while revolving 200,000 times a minute. 
If a firebrand be whirled, in the dark, round a centre in a plane 
perpendicular to the eye of the spectator, it will present the appear¬ 
ance of a luminous circle. From this fact it has been inferred, that 
the impression on the retina made by the luminous body in its pas¬ 
sage through every point of the circle, remains until the body has 
completed a revolution. How rapidly soever the firebrand may be 
made to revolve, the circle, and therefore every part of it, will be 
distinctly visible: hence a probability arises, that at the greatest at¬ 
tainable velocity a perfect impression of the object in motion will 
still be produced on the optic nerve, provided that the time of view¬ 
ing such object be limited to that which is required for passing 
through a small space—small, at least, with reference to the size of 
the revolving body,—and also that no other object be presented on 
the field of vision before the former spectrum shall have vanished 
from the eye; unless in the case of the same object under similar 
circumstances. The former of these conditions is provided for in 
machine No. 1, in which the eve-hole is made to travel through 
180 feet between every two inspections of the moving object, and 
which object is made to assume a different position at each succes¬ 
sive inspection. The latter condition is included in machine No. 2; 
the object is there presented to the eye in one position only. 
STATISTICS. 
On the Statistics of the Dublin Foundling Hospital , and on Child 
Desertion in the City of Dublin. By Henry Maunsell, M.D „, 
Professor of Midwifery to the Royal College of Surgeons in Ire¬ 
land, and Ordinary Member of the Medical Society of Leipzig. 
During thirty-four years, comprised between 1798 and 1831 (in¬ 
clusive), there were admitted 51,523 children. Of these, 700 were 
immediately restored to their parents, and 12,153 died immediately 
in the nursery. These latter must be considered as having been 
destroyed by the act of desertion, and therefore cannot fai rly be 
charged to the account of the hospital. 
