The object of the other parts of the instrument are to secure regularity in its operation by keeping the level of the liquid constant. It is evident, in fact, that if the level of the water gets below _r_, the capacity of the buckets will be increased, and the counter will indicate a discharge less than is really the case, and _vice versa_. If the level descends as far as to the orifice in the partition, _hh'_, the gas will flow out without causing the apparatus to move. The water is introduced into the counter through _f_, which is closed with a screw cap, and passes through the opening shown by dotted lines into the reservoir, RR', whence it flows to the box, BB', When it has reached the desired level, it gains the orifice, _r_, of a waste pipe, escapes through the siphon, _ruv_, and makes its exit through the aperture, _b'_, when the screw cap of the latter is removed. If, by accident, the level of the water should fall below a certain limit, a float, _f_, which follows its every movement, would close the valve, _s_, and stop the flow of the gas. Finally a tube, _tt'_ soldered to the lower part of the tube, _lnl'_, and dipping into the water of a compartment, P, serves to allow the surplus water to flow out at _b'_. To prevent the apparatus from being disarranged upon the drum being revolved in the opposite direction, there is fixed to the axle, _aa'_, a cam which lifts a click, _z_, when the rotation is regular, but which is arrested by it when the contrary is the case.--_Science et Nature_. * * * * * DOBSON AND BARLOW'S IMPROVEMENTS IN HEILMANN'S COMBERS.