Measurement of changes in the dimensions of Solid Bodies. 447 
At M, fig. 3, is a milled head for winding up the brass wire 
attached to the lower copper strip and thus bringing the pendu- 
um into a horizontal position, i.e., its real object being to ad- 
just the mirror of the pendulum with regard to the scale and 
telescope 
a lead-penci 
Micrometer.—The left-hand rear screw, I, fig. 4, was used as 
a micrometer ; it rested on a small leveled plate of glass and 
was provided with an arm 140 mm. in length, which was capa- 
ble of moving over $ or } of a degree of arc between two 
of the lever-arm was measured with a compound microscope 
placed over its extremity ; the length of this arm being known, 
and the number of threads of the screw, the actual upward 
motion could be calculated. 
At B, fig. 3, is a counterpoise, its object being to remove 
most of the pressure from the micrometer screw. 
Scale and Telescope-—A glass scale divided into agg 
tinuously during most of the day and the greater part of the 
night. Hence, in spite of the oil-box, the pendulum was never 
completely at rest, except for three or four hours after mid- 
night: during the day-time the vibrations were often so rapid 
