PHOTOGRAPHY TO METEOROLOGY. 
167 
APPENDIX. 
Instruction's op the British Association Committee on Meteoro¬ 
logical Photography. 
Photographs are desired of clouds, lightning, hoar-frost, remark¬ 
able hailstones, snow-wreaths, avalanches, glaciers, storm-waves, 
waterspouts, tornadoes, dust-whirls, halos, parhelia, or of any other 
meteorological phenomena or their consequences. 
General Instructions. 
1. As soon as possible after exposing a plate, number it and fill 
in the details relative to it on one of the forms supplied. The 
more completely these are filled in the more valuable will the 
photograph be. 
2. The size of the plate is immaterial provided that the focus is 
sharp. IJse a magnifier when focussing, and for objects like clouds 
focus upon a distant tree or building. 
3. TJse a lens which does not distort the image. 
4. Do not touch up either negative or print. 
5. When photographing any object which is moving or changing, 
a series of views taken at short intervals, so as to show the progress 
of the phenomenon, will be of especial value. 
6. Whenever possible, a figure or other object of known dimen¬ 
sions should be introduced, in order to serve as an approximate 
scale. 
Cloud Photography. 
Eor heavy clouds no special apparatus is required, but exposure 
must be shorter than for ordinary landscape work. Eor very thin 
clouds exposure must be extremely short and development very 
cautious. Eair results may then be occasionally obtained without 
special means. 
In order to obtain better and more certain results three methods 
have been adopted 
(a) Using a slow plate and rapid lens, with short exposure. 
( b) Using an ordinary plate and lens, but with a sheet of pale 
yellow glass in front of the lens. 
(c) Using an ordinary plate and lens, but placing a plane mirror 
of black glass in front of the lens so that its surface makes an angle 
of about 33 degrees with the axis of the lens. The image reflected 
in the mirror is fairly easy to photograph. 
The Committee hopes to receive examples of each of these pro¬ 
cesses, as well as examples and descriptions of any other special 
devices which may be adopted by observers. 
Lightning Photography . 
When a thunderstorm occurs at night it is very easy to photo¬ 
graph the flashes of lightning. 
