hydrochloric acid, a solution from which considerable quantities of
arsenic and several other metallic salts may be precipitated.
Commenting on this fact, ascertained by M.A. Jorissen, M. Francis Maur
asks whether this breathing of arsenic and other minerals in a finely
divided state may not account for the singular immunity from epidemics
enjoyed by certain industrial districts, such as that of Saint
Etienne, and hopes that some mine doctor will throw additional light
on the subject. In the meanwhile, it may be suggested that the
ventilating effect of the numerous chimneys in iron making and other
industrial centers has its due share in constantly driving off the
vitiated air and replacing it by fresh quantities of pure air. At any
rate, when pestilence was raging in the high and pleasant quarter of
Clifton, its inhabitants migrated to the low-lying and not overclean
parish of St. Philips, Bristol, where the air is black from the smoke
of numerous chimneys, but where also the mortality compared very
favorably with that in the fashionable quarter.

A TWO-SPEED movable sidewalk, of the Blot, Guyenet and De Mocomble
type, is to be used for conveying visitors at the Paris Exposition,
says Engineering News. It differs from those of Chicago and Berlin in
the reduction of the weight of the moving platform by spacing the
driving wheels 127.5 feet apart and using electricity as a motive
power. The driving wheels are mounted in the bed of the track and
impart motion to a central rail on the under side of the platform.
Bearing wheels, spaced about 20 feet apart under this rail, also carry
the platform, and the central rail supports one-half the total weight
of the platform; small side wheels carry the other half on side
tracks. This arrangement enables the platform, which is divided into
sections and hinged, to pass around quite sharp curves. The high speed
platform, 4 feet 3 inches wide, is supposed to move at the rate of