462 TransacUons .—Miscellaneous . 



like the details, the picturesque combiuatiou first observed has 

 vanished, and something totally different has taken its place. 

 This must have been the experience of many amateur and 

 professional photographers besides myself. 



To meet and overcome such difficulties lenses of more than 

 ordinary focal length might be used. Lenses of 25in. or of 

 30in. focal length would, no doubt, to some extent satisfy the 

 j'equirements of the object in view ; but, as such instruments 

 require the use of cameras of a corresponding extension, the 

 apparatus would prove cumbrous, unwieldy, and also unstable 

 should the weather be at all windy. 



Some of these difficulties it has been attempted to over- 

 <,'ome by the use of an ordinary telescope attached to and 

 placed in front of the lens ; but at first sight it nmst be evi- 

 dent that this is a very doubtful improvement, involving as 

 it does the support of the telescope and otherwise the un- 

 steadiness of the sliding parts. Besides, the results are not 

 what should be aimed at. The picture resulting, though 

 sharp in detail, is of small size, and requires the after-process 

 of enlargement, which may or may not be successfully accom- 

 plished. 



Some years ago I set myself the task of producing tele- 

 scopic pictures, and at first I used an ordinary achromatic tele- 

 scope having positive focus ; but, for the reasons already 

 pointed out, I soon discovered that this could be of no use as 

 a;pj)lied to the purpose I had in view, and it became evident 

 that what was wanted v^as a telescope of considerable power, 

 but having a very short focal length. As meeting the re- 

 quirements of the case, and serving the purpose I had in 

 view% I made use of one tube of an opera-glass of small 

 size. This, placed in front of the photographic objective, 

 gave a much larger picture than that obtained by using the 

 longer-focussed telescope with positive focus. I next mounted 

 the lenses, the objective and eyepiece, in separate tubes, sliding 

 one into the other, so that this part could thus be focussed, 

 and afterwards fixed the wliole to the case of a single achro- 

 matic photographic lens. With this, and by varying the 

 power of the biconcave eyepiece-lens, I obtained pictures of 

 different scales, varying in size from a quarter-area to that of a 

 half-plate. At the same time I also found that, by a slight 

 a;djustment of the telescopic part, focus on the camera-screen 

 could be obtained at any distance, from near contact with the 

 back lens to the furthest extension the camera was capable 

 of, and this with a corresponding increase of the scale and size 

 of the picture as the length of the camei'a-screen was greater 

 from the back lens of the instrument. 



I could now produce pictures of almost any :^ize, but they 

 were lacking in vigour, and were not quite as sharp as I de- 



