GARDEN MECHANICS. 
79 
For the construction of the instrument advantage has been 
taken of the expansive properties of wood when wetted—a thin 
slip of mahogany being the motive power, which, acting by 
means of a silken thread passed over an axle, gives motion by its 
contraction in drought to a hand like that of a clock, and this, 
by working over a dial plate, marks the amount of moisture 
which surrounds it. Its action is instantaneous with any change 
in the atmosphere. In an Orchidaceous house it marked in the 
morning 35°; in order to test it, the instrument was taken into 
the boiler shed, where it shortly drew round to 90°, and on re¬ 
turning it to the house it again resumed the original position. 
In the middle of the day the sun shone brightly, and a portion 
of fresh air was consequently admitted into the house, which 
caused an immediate abstraction of moisture to'the amount of 25° 
by the instrument. The value of such an invention is scarcely to 
be appreciated, and we predict it will prove a severe test to many 
of the existing modes of heating, if it does not cause an entire 
alteration of the means employed. 
Under this head we may also mention the improved hydraulic 
ram of Mr. Roe—not as a thing absolutely new, but as an ex¬ 
tremely useful auxiliary to that vitally essential adjunct to every 
establishment, a good supply of water. The immense expendi¬ 
ture of both time and money in the laborious operation of pump¬ 
ing is incalculable; in many places where, too, at a short dis¬ 
tance, a large volume of the fluid is absolutely running away, 
without affording the slightest benefit to its possessor. In 
such places, or wherever a fall of a few feet can be obtained from 
the head of water, and the means of providing for the escape 
of the waste, a ram of this description will afford a constant 
supply, without the least manual assistance. We subjoin an 
account of it: te Since the original introduction of the hydraulic 
ram of M. Montgolfier, many suggestions for its improvement 
have been made and adopted. The first essential improvement 
was that made by his son, and secured by patent in this country. 
The operation of the latter was much more effective, amounting 
to no less than eighty-four per cent., whilst the length of the 
tube was much less than in the original machine. These im¬ 
provements consisted in the addition of a small shifting valve, 
which serves to introduce a quantity of air into the head of the 
