120 PHOTOGRAPHING LIGHTNING WITH MOVING CAMERA. 



strata of clouds, therefore the best time for obtaininc: photoo-raphs 

 is either at the beginnino' or the end of a storm. At the beginning 

 the wind is usually very strong, hindering the work, so that it is gener- 

 erally best to wait imtil the front of the storm has just passed overhead 

 and then to expose the camera from a windoAv or other suitable place 

 facing a direction opposite to that of the wind. In this way the 

 camera as well as the person will be protected from the wind and rain. 

 This rule holds good in most cases, although there are many excep- 

 tions, especially when the storm is local in character and of small 

 extent. A j^erson must be on the lookout at all times and note the 

 direction in which most of the downward strokes appear and direct 

 tlie camera toward them. 



It is useless to expose plates when there is nothing but sheet light- 

 ning, for it will only result in spoiling them. Oftentimes there is a 

 mixture of sheet lightning and a few scattered ground strokes at 

 uncertain points. "When that be the case, the chances for obtaining 

 pictui'es are slight, the sheet lightning soon fogging the plates, the 

 time for fogging in such cases l)eing from five to ten minutes, depend- 

 ing on the frequency of the reflections. The best rule to follow is to 

 wait until a favorable opportunity presents itself, when the flashes 

 are about half a mile distant, then act quickly, have plenty of plates 

 ready to insert in place of the exposed ones, and trust to luck. The 

 best way of holding the camera when swung by hand is to place it 

 close to the body, tilting it somewhat upward, so as to get as much as 

 possible of the sky in the picture, and swinging the body from side 

 to side. The time and angle of the swing can be regulated with a 

 little practice so as to be fairly accurate, say one second to the swing, 

 although the writer has found by experience that when a sudden 

 flash appears in front of the camera the evenness of the swing will be 

 somewhat disturbed, particularly if the flash is close to the observer, 

 unless the person l)e in possession of unusually strong nerves. When 

 pictures of horizontal flashes are desired the camera must naturally 

 have an up and down swing. These flashes are usually less intense 

 and the pictures of them sometimes require a very long time to 

 develop. 



The developer preferred by the writer is " Rodinal,'' being con- 

 venient and clean, although any good developer will do, jiarticularly 

 such contrast developers as " Glycin " or " Hydrochinon." 



Dirt'erent kinds of plates have been tried, but the writer has no 

 special preference for any one of the standard plates. The ortho- 

 chromatic plates do not seem to give l)etter results than the ordinary 

 ones. Films give trouble in developing, because each exposure must 

 ])e developed separately. 



I'igure 9 shows the barometer devised by the writer, which he has 

 found very useful in the study of the variations of the atmospheric 



