406 REPORT— 1895. 



copies fi'om negatives is seen in the fact that some of the prints 

 received at an early period of the collection have faded. In many 

 cases, too, the earlier photographs have been replaced by better prints 

 of the same subject. From these and other causes, the number of 

 photographs which have been mounted and placed in the portfolios 

 provided by the Committee is somewhat less than that given in the 

 above summary. 



The Committee have made special efforts during the year to obtain 

 contributions of photographs from localities not hitherto represented in 

 the collection, and have again issued a circular to the delegates of the 

 Corresponding Societies and to a large body of geologists and photographers 

 in the United Kingdom. All the responses which were expected have 

 not yet been received, owing, in great measure, to the fact that it is often 

 difficult (especially in those of our inland districts situated far away from 

 large towns) to obtain the services of a skilled photographer having 

 sufficient geological knowledge. 



In addition to the usual recommendations for the collection of photo- 

 graphs, the Committee issued a 'precis (given below) of the letters con- 

 taining suggestions for suitable cameras sent by several members who 

 were invited to state their views on this subject, as mentioned in the last 

 Report. It is hoped that these hints on the selection of a suitable camera 

 for geological field work may be useful to many geologists who desire to 

 have their own photographic records of scenic features or sections of 

 interest. 



Apparatus for Geological Photography. 



The best camera to use is probably that to which the woi'ker is himself 

 most accustomed. These hints are added for the guidance of those who 

 have not yet adopted any particular camera. 



The camera should be as light as possible, but rigidity when set up is 

 absolutely necessary. 



Double swing-back and rising and falling front ai-e essentials, to allow 

 of correct perspective and the true rendering of lines and curves. 



The camera should admit of long extension to permit the use of lenses 

 of various ybci. 



It is sometimes desirable to take photographs of inclined or horizontal 

 rock-surfaces at distances of a few feet, for the purpose of showing minor 

 features, such as veins, glacial markings, structures of gneissose rocks, &c. 

 To effect this, two boards hinged together with some arrangement for 

 fixing them at the desired angle are all that are required. The lower 

 board must, of course, be screwed to the stand and the upper one to the 

 camera. 



A spirit level should be attached to or used with the camera. 



It is well to have three lenses : — (1) A rapid rectilinear doublet of 10 

 to 12-inch focus (for ^-plate size) ; (2) a wide-angle meniscus, focal 

 length about 6 to 7 inches, for interiors of quarries and craters ; and (3) 

 a long-focus lens of focal length equal to three or four times the length of 

 the plate, for distant hills and inaccessible cliffs. 



If only one lens is used, it should be a rapid rectilinear of about 9-inch 

 focal length (for | -plate size), and should be by some reputable maker. It 

 must be the best of its kind obtainable. Though films materially decrease 

 the weight to be carried, they are not recommended for general use : 

 plates should be used whenever possible. Good general work can be done 



