valves, on the contrary, have only one guide each, which passes upward
through the seat of the admission valve, through the valve itself by
means of a collar, and through the stuffing-box. It is furnished with
hard steel armatures, through which the levers, z1 z2, Fig. 3, act upon
the exhaust valves.

[Illustration: BORSIG'S IMPROVED COPOUND BEAM ENGINE. FIG. 4]

The governor effects the acceleration or retardation of the loosening of
the catch actuating the steam valve by means of hard steel projections
on the shaft, v1, the position of which, by means of levers, is
regulated by the governor, which in its highest position does not allow
the lifting of the inlet valve at all. The regulation of the expansion
by the governor from 0 to 0.45 takes place generally only in the case of
the high-pressure cylinder, while the low-pressure cylinder has a fixed
rate of expansion. Only when the low-pressure cylinder is required
to work with steam direct from the boiler is the governor applied to
regulate the expansion in it. An exact action in the valve guides and
a regular descent is secured by furnishing them with small dash pot
pistons working in cylinders. Into them the air is readily admitted by
a small India-rubber valve, but the passage out again is controlled at
pleasure.--_The Engineer_.

* * * * *

TO DETECT ALKALIES IN NITRATE OF SILVER--Stolba recommends the salt
to be dissolved in the smallest quantity of water, and to add to
the filtered solution hydrofluosilicic acid, drop by drop. Should a
turbidity appear an alkaline salt is present. But should the liquid
remain limpid, an equal volume of alcohol is to be added, which will