Sept. 28, 1871] 
NATURE 
431 

thermometers, and thus shows the atmospheric pressure, 
the temperature of the atmosphere, and its hygrometric 
condition—z.¢., its condition of moisture or dryness. 
The engraving, Fig. 8, is a perspective view of this 
instrument. The recording lever, A, is a bar of iron 
about two feet in length, nearly balanced on the axis, 
supported by the clock-frame, C. The clockis constructed 
with rather stronger gearing than an ordinary movement, 














































its office being to elevate and depress the lever A hourly, 
regulate the drum, D, and raise the two striking hammers, 
Hand H’. It is provided with a half-second pendulum, 
and requires winding once in two days, the weight drop- 
ping in that time about three feet. 
The shorter leg of the siphon barometer is shown at B, 
and the wet and dry bulb thermometers at T’ and T. 
Directly over the leg of the siphon, as also over the two 
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FIG. 8,—THE METEOROGRAPH 
thermometers, the lever A supports a carriage, which is 
depressed or elevated whenever the lever A is in motion. 
The registering point, G, is connected with the lever, as 
shown in the diagram ; and the curvilinear motion of the 
end of the lever is converted into rectilinear by allowing G 
to slide against a vertical steel rod. 
To illustrate the action of the machine, we will suppose 
the lever A has reached its lowest point, the registering 
| pen G being at the Lottom of the drum. Now, in order 
| that we may be able to register the barometer on any part 
| of the drum sheet, it is necessary that the striking hammer 
| should be elevated and locked before the upward motion 
| of the lever commences. As the hammers are raised by 
means of an arm carried by the hour shaft of the clock, at 
the point where the hammers begin to rise the snail for 
| elevating the lever A is cut away, so that it remains at 
