296 Scientific Intelligence. 
IV. ASTRONOMY AND METEOROLOGY. 
n 
that of Mercury in transit. M. LeVerrier thinks the observation worthy 
of credit, and computes that on the supposition of a circular orbit the 
- time of the planet’s revolution around the sun is 1947, and the inc 
tion of its orbit 12° 10’. Its greatest elongation from the sun would 
~ 
: : ° + but it 
essentially the same as that of the parallel-wire micrometer ; pode 
its wide range depends. eee a 
The most remarkable of these peculiarities consists in its being pio ¥ 
a ngle 1 dis 
with two eye-pieces, composed of small si ses, mounted in S¢ die 
es . . : the required 
frames, which slide in a e, can be separat pact ounted sf 
_ of the eye-pieces; and, by a free motion in this frame, each web 2 
Opposite to its own eye-lens. on aa’ 
In using this micrometer, the first step is, to set the position-ser be : 
the approximate position of the objects to be measured. TH, 
eye-lenses are separated till each is opposite to its own object. slid into ib 
a webs and their micrometer-screws *, at their prope’ 
Ha-3 and, the webs having been separated nearly to # on the 
distanee by their free motion in the frame, they are placed precisy 
Objects by their fine screws, the observer's eye being ¢ Hisection . 
‘ ae to the other a few times, till he is satisfied of the removed 
of the objects by its own web. The frame is then a 
