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HARDWICKE'S SCIENCE-GOSSIP. 



[Oct. 1, 1S66. 



PHOTOGRAPHY. 



Printing in Carbon.— Mr. Swan's new process 

 for book illustrating, the difference between which 

 and Mr. Woodbury's process we cannot discover, 

 has recently been used for putting into circulation 

 some thousands of copies of Mr. D. 0. Hill's 

 painting of the "First General Assembly of the 

 Eree Church of Scotland." These re-productions 

 are singularly perfect and beautiful, and fully justify 

 the artist in substituting Mr. Swan's beautiful 

 process for that of engraving, by which it was ori- 

 ginally intended to be copied. The celerity with 

 which these copies were executed speaks well for the 

 working character of Mr. Swan's process, and we 

 give full credit to the Newcastle Daily Chronicle, 

 which asserts "that the field is boundless which 

 lies before the carbon process of our ingenious 

 townsman Mr. Swan." — /. W. W. 



Photography at the British Association. — 

 Many old jokes are based upon the ease with which 

 the simplest and most common-place things may be 

 surrounded with many-syllabled technicalities, so as 

 to assume an importance comically at variance with 

 their real nature. We fear the long paper read by 

 M. Claudet in section A of the British Association, 

 although advocating what its author designated 

 "the greatest improvement which will have been 

 introduced in photography," may recall some of 

 these old jokes to its readers' memories. This paper 

 described a little obsolete technical " dodge," intro- 

 duced before lenses were manufactured to do actually 

 aud legitimately what M. Claudet's "new process," 

 as it appears, is merely supposed to do. It consists 

 of moving the lens in or out of the camera during 

 the exposure of the plate, so that the various planes 

 of distance represented are alternately in and out of 

 focus. The object in so doing is to distribute the 

 definition more equally and insure greater softness. 

 But M. Claudet appears to have overlooked many 

 objections to such a plan. The impossibility of 

 regulating the degrees of sharpness with sufficient 

 exactness, and that of so dividing the time of 

 exposure as to allot to the in-focus and out-of-focus 

 images their respective degrees of action on the 

 plate, are all we need call attention to, as these in 

 themselves suffice to demonstrate the impractica- 

 bility of such a scheme. But there is something 

 more to be said on this subject. That the photo- 

 graphic lens in its working should approach as near 

 as possible " the beautiful instrument which gives 

 to man the most perfect perception of all the 

 wonders and beauties of nature," is of course to be 

 admitted, although it must not be forgotten that 

 what we see depends as much upon our powers of 

 perception as upon the possession of sight, and that 

 something more than eyes are required for "the 

 most perfect perception of all the wonders and 



beauties of nature." Admitting this, we ask, Does 

 the eye see all things near and remote with equal 

 distinctness ? No one will be hardy enough to say 

 it does, and such being the case, why should we so 

 alter our lenses as to make them give figures in which 

 all parts are equally in or out of focus ? The lens 

 which gives one plane sharply in focus, and all 

 other planes out of focus, is preferable to this, and 

 its images are more nearly related to those seen with 

 the human eye than are images in which every part 

 on every plane of distance is equally out of focus. 

 The concentrated nature of images thrown by the 

 lens undoubtedly originates in photographs that 

 hardness, miscalled sharpness, of which we have 

 heard so many complain. But there should be 

 behind the camera of the photographer, as there is 

 behind the camera of the eye, that power of percep- 

 tion to which the recognition of nature's " wonders 

 and beauties" is truly and mainly due ; and where 

 this is the case, with any good lens true and beautiful 

 images may be reproduced without having recourse 

 to the awkward and unsatisfactory shifts M. 

 Claudet recommended in his paper "On a New 

 Process for Equalizing the Definition of all the 

 Planes of a Solid Figure represented in a Photo- 

 graphic Picture."—/. W. W. 



A New Magnesium Lamp. — In section B of the 

 above-named association, Mr. H. Larkin exhibited 

 a new patent magnesium lamp, which photographers 

 will very gladly welcome, inasmuch as those now iu 

 the market are not so satisfactory as it is desirable 

 they should be. The distinguishing peculiarity of 

 the new lamp is, that it burns the metal in the form 

 of powder instead of ribbon or wire ; and its chief 

 advantage is, that it renders the unsatisfactory clock- 

 work arrangement hitherto used unnecessary. A 

 large reservoir holds the powder, which falls by its 

 own gravity, like sand in the hour-glass. To insure 

 its burning with a steady continuous flame, fine sand 

 is mixed with the metal in quantity proportioned to 

 the strength or size of the flame desired. After 

 leaving .the reservoir, the stream of mingled sand 

 and magnesium flows through a metal tube, into the 

 upper end of which is introduced a small jet of 

 ordinary gas, which being turned on, is lighted, and 

 then these mingled streams escaping from the mouth 

 of the tube together, burn with a powerful light so 

 long as the magnesium lasts. The fumes are con- 

 veyed away through a chimney, and at the same time 

 the sand falls harmlessly into a receptacle provided 

 for it. The flow of the inflammable material may be 

 cither regulated or arrested by the opening or closing 

 of a valve. The cost of burning this lamp is said to 

 be about twenty shillings an hour.—/. W. W. 



"Mournful Numbers."— The penny weekly 

 issue of romances about highwaymen and robbers. 

 — Fun. 



