292 Proceedings of Societies. 
without its aid would escape observation. Copies of the two totality pic- 
tures are being made to illustrate Mr De La Rue’s paper in the report 
of the Himalaya Expedition by the Astronomer Royal. Positive 
enlarged copies of the phases of the eclipse, 9 inches in diameter, have 
also been made by means of the camera, and were exhibited at the 
Manchester meeting. 
The heliograph has since been replaced in the Observatory, but few 
opportunities have occurred for using it, in consequence of the pressure 
of other work ; latterly, however, Mr Beckley has been requested to carry 
on some experiments with the view of ascertaining whether any more 
details are rendered visible when the full aperture of 3 inches of the 
telescope is used, than when it is reduced to about one inch and a-half. 
Up to the present time no definite conclusion can be drawn from the re- 
sults obtained ; so that, at all events, an increase of aperture does not ap- 
pear to give a strikingly better result when a picture of the same size is 
taken with various apertures of the object-glass, More experiments, 
however, are needed before this point—which is one of some importance 
in guiding us in the construction of future instruments—can be answered 
definitely. Mr Beckley has obtained sun pictures of great beauty during 
the course of these experiments. 
The work of the Kew Observatory is now so increased that it has be- 
come absolutely imperative to make some provision for working the helio- 
graph in a way that will not interfere with the current work of that 
establishment; and Mr De La Rue has been requested by his colleagues 
of the Kew Committee to take charge of the instrument at his observatory, 
where celestial photography is continously carried on. This request Mr 
De La Rue has kindly acceded to; and he will for a time undertake to 
record the sua spots at Cranford, as long as it is found not to interfere 
with his other observations. Mr De La Rue has contrived, and had 
made by Messrs Simmis, at his own expense, an instrument for measur- 
ing the photographs, which will much facilitate the reduction of the re- 
sults. It consists of a fixed frame, in which work two slides, moving at 
right angles to each other. Each is furnished with a vernier reading to 
roos th vf an inch. The top slide works on the lower slide, and carries a 
hollow axis 43 inches diameter, on which rotates horizontally a divided 
circle reading to 10”, and this carries a second circle on the face of which 
are fixed four centering screws. An image intended to be measured is 
placed on the upper circle, and is centered by means of the adjusting 
screws ; it is then adjusted by means of the upper circle in any required 
angular position with respect to the lower divided circle, so as to bring 
the cross lines of the photograph in position under a fixed microscope, 
supported on an arm from the fixed frame. By means of this instrument 
the sun pictures are measured so as to determine the diameter to z7y5th 
of the radius; tle angular position of any part of a sun-spot, and its dis- _ 
tance from the centre, are thus readily ascertained ; or the differences of 
the right ascension and declination with respect to the centre are as easily 
read off to the same degree of accuracy. 
Mr De La Rue has recently produced by his large telescope an image 
of a solar spot, and portion ot the sun’s disc, far superior to anything be- 
fore effected, and which leads to the hope that a new era is opened in 
heliography, and that the resources of this observatory might be further 
developed in that direction. 
In the evening the President delivered his inaugural address in the 
Free Trade Hall, which, spacious as it is, proved too small to accommo- 
date the multitude who came to hear him. He confined his attention 
chiefly to the application of science to the arts, celebrating in a very 
courtly manner the members of the Association, as often as the introduc- 
