. TRANSACTIONS OF THE SECTIONS. 13 
the direction of the wind is at once the cause and the indication of changes of the 
_ weather. However far we may be from a general solution of the problem of atmo- 
spheric disturbances, meteorologists have made considerable progress in tracing the 
- connection hetween successive states of the weather, owing to the mutual influence 
of contiguous portions of the atmosphere. These cases have been studied @ posteriori, 
comparing the known results with observations extending over considerable areas. 
Now that we have the means of receiving information in an indefinitely short space 
of time by the Electric Telegraph, these problems, under favourable circumstances, 
* may be studied @ priori. In London we may receive instantaneous intelligence of 
the condition of the atmosphere, as to the five above-mentioned elements, from 
nearly all the extremities of Great Britain. With a delay of about four hours we 
can have similar intelligence from the western part of Ireland, and with a still 
shorter delay our communications may. extend to the centre of France, the banks of 
the Rhine, and even to the frontiers of Hungary and Poland. 
I do not pretend to say that with such elements for calculation we should at once 
be enabled to predict changes in the weather with absolute certainty. It would re- 
quire some time to eliminate the action of accidental and local causes at particular 
stations; but there is no reason to doubt that in a short time the determinations 
thus arrived at would possess a high degree of probability. The ordinary rate at 
which atmospheric disturbances are propagated does not seem to exceed twenty miles 
per hour; so that with a circle of stations extending about 500 miles in each direc- 
tion, we should in almost all cases be enabled to calculate on the state of the wea- 
ther for twenty-four hours in advance. 
— 
Description of a New Instrument for observing the Apparent Positions of 
Meteors. By the Rev. J. Cuaruts, MA., F.R.S., Plumian Professor of 
Astronomy at the University of Cambridge (in a Letter to the Assistant 
General Secretary). 2 
Having had occasion to make use of observations of auroral arches and corone, 
and other meteoric phenomena, I have seen the desirableness of noting the posi- 
tions by instrumental means, rather than trusting to vague estimation and reference 
to stars. Accordingly I have had a brass instrument constructed for me by Mr. 
Simms, Fleet Street, London, which may possibly answer this purpose in some 
degree. I propose to call it a Meteoroscope. It is in principle an altitude and 
azimuth instrument, in the form of a theodolite, having a horizontal circle graduated 
from 0° to 360°, and a vertical arc graduated from 0° to 120°, each about 4 inches 
in radius. The vertical arc is readily moveable about a vertical axis passing through 
the centre of the horizontal circle, and instead of having a telescope, which would 
be inapplicable to,the class of observations proposed to be taken, it carries a bar 
18 inches long, having’a small rectangular plate at each end. One of these plates 
is perforated by a circular hole one-sixth of an inch in diameter, through which the 
object is viewed, and the other has its edges vertical and horizontal, the observation 
of altitude being made by bringing the horizontal edge, and the observation of azi-- 
muth by bringing the vertical edge, to bisect the object. Both observations are 
made at the same time by placing the angular point in apparent coincidence with the 
object. The eyelet-hole should not be less than the pupil of the eye when dilated, 
that there may be as little loss of light as possible. No parallax of serious amount 
will arise from the size of the hole, as it is always easy to judge when the centre of 
‘ the pupil and that of the hole are nearly coincident. The bar is moveable about a 
horizontal axis passing through the centre, and perpendicular to the plane of 
the vertical arc, and is carried by a radius so that the direction of its length is a 
tangent to the arc. The direction of the radius is somewhat oblique to that of the 
bar, in order that the line of collimation may pass the zenith about 20° when the 
radius is brought to a horizontal position. For the same reason the centre of mo- 
tion of the bar is elevated about an inch and a half above the plane of the azimuth 
circle. For the purpose of viewing conveniently an object near the zenith, the 
plate at the eye-end of the bar has a small silvered glass reflector inclined at an 
angle of 45° to the plane of the plate, and adjustible by a screw. The object is seen 
by reflexion in a direction perpendicular to the line of collimation, through another 
