THE ESSEX FIELD CLUB.
41
of the whole exposure, so that solid objects were seen through the figure in the
resulting print.
In astronomical photography, Professor Meldola stated, dry plates are par-
ticularly useful, and they are now being employed for an international survey of
the heavens. He here exhibited two fine slides by Mr. Isaac Roberts, a pioneer
in such work. The one photograph represented a nebula in the constellation of
the Little Dog, and the other the Great Nebula in Orion. In these, he pointed
out, were also great numbers of stars, and among them some invisible to the
human eye, except by the aid of photography. Photography has also revealed
the fact that some objects, hitherto classed as stars, and mapped as such, are in
reality small nebulae. These photographs had been taken with a reflector, and
not with a lens, with an exposure of four hours, and by using most delicate
appliances to enable the telescope to follow accurately the apparent motions of
the heavenly bodies without vibration. The exposure given in taking each of
the nebulas was four hours. An American astronomer once spent many years in
drawing the Great Nebula in Orion. He next exhibited another photograph, by Mr.
Roberts, of a beautiful nebula in Andromeda, which also was taken with a reflector.
Photography might also be used for securing records of natural phenomena.
He projected on the screen two slides, representing the river at Wakefield in its
ordinary condition, and during the flood of 1892. These, and some other slides,
belonged to a committee of the British Association, which is collecting photo-
graphs of meteorological phenomena ; the slides had been lent to him by Mr.
Symons. He exhibited also frost and snow scenes, and said that recently some
beautiful photographs of snow crystals have been taken on the Continent. When
dealing with cloud photography he described Mr. Clayden's work, and projected
specimens on the screen. He also exhibited a striking photograph of the Malvern
Hills, the crests only projecting above the mist, which latter seemed rolling
onwards like a great sea. Photographs of lightning flashes were then exhibited,
one by Mr. Frank Hughes, showing that flashes are not always single, and that
several flashes may occur from different parts of a cloud at the same time. He
said that lightning flashes are sometimes double, and that separate images are
sometimes obtained by moving the camera while the electrical discharge takes
place.
Another Committee of the British Association is now using photography in
making an ethnographic survey by Mr. Francis Galton's method, to add to the
stock of information about race characteristics. Photography is also used in aid
of archaeology, and sometimes to give evidence relating to disputed points. For
instance, various prehistoric temples are supposed to be "oriented," so that the
chief altar directly faces the rising sun on the longest day—the summer solstice.
The lecturer exhibited a slide of the rising sun at Stonehenge on the longest
day of the year, taken from what is assumed to have been the most sacred
part. The sun then appeared on the apex of a huge stone, called the Friar's Heel,
and chanced on that particular morning to be surrounded by a halo, so as to make
a striking picture, seen through the "bridge," if so it may be called, formed
by two perpendicular stones in the foreground, between them supporting one huge
stone on the top. The lecturer next spoke of the way in which photography is being
utilised by the Geological Photographs Committee of the British Association,
and showed some slides lent by the Secretary to the Committee, Mr. Jeff's, repre-
senting inland erosion by wind and water, the erosion of sea coasts, the formation
of caverns, the nature of basaltic formations, and the records of glacial action in
former times preserved by certain rocks. He exhibited a photograph of part of