344 T, V. Shcherbakova 



For the lamps installed in the camera (the power of a single lamp is 5 candle 

 power) and the distance of 20 cm from them to the subject of the photograph, 

 the illumination of the subject (allowing for absorption) is about 6 lux. For 

 this ilhmiination the exposure time A\dth a film speed of 45 GOST units 

 equals 7 sec. 



Test photographs of plates showed that the resolving poAver of the well 

 camera mth the lower part of the instrument not filled with water is about 

 30 lines per mm, and when filled with water about 10 lines per mm. This 

 resolving power ensures that rock grains of size 0.1 mm and greater can 

 be distinguished. The reduction of resolving power when the lower part 

 of the instrument is filled is associated with the scattering of light in the 

 water filhng the lower part of the instrument. 



Figure 9 shows a photograph by the well camera of a test plate (photograph 

 taken in water). 



Corrosion of components in the lower part of the instrument filled with 

 water caused great difficulties. To avoid this and to increase the resolving 

 power it is proposed in the future not to fill this part of the instrument with 

 water but to fix thick glass into the viewng window and provide it with 

 reHable hermetic seahng. 



PHOTOGRAPHY OF ROCKS ALONG THE WALL OF A WELL 



The well camera described above was used to take photographs in wells 

 8,9 and 10 of one of the sites of the South Kazakhstan region and in well 

 2089 in part of the work of the Kamenskaia geological survey party in Donbass. 

 The wells were filled with clear water. 



In wells of a site in the South Kazakhstan region the well diameter is 

 90 mm. Photographs were taken at depths from 40 to 150 m in wells 8 

 and 9, and from 23 to 80 m in well 10; in all, one hundred photographs of 

 the rock were obtained. The section consists mainly of dolomites and 

 argilHtes. 



From the photographs it is usually possible to establish the lithological 

 nature of the rock. Dolomites are distinguished by nodular irregularities 

 with sharp contours, associated with the special nature of the fractures 

 of this rock. In some cases the fine-grain structure of dolomite is over- 

 looked. 



The argillites are distinguished by the presence of erosion, marked by 

 shadows and breaks in the sharpness of the image. 



Brecciated rocks are clearly detected ; on a photograph the rock fragments 



