164 I NDULATORY FORCES. LIGHT PHOTOGRAPHY. [OBUHU* lB0numr. 



mean* already referred to, and have a more intimate 

 Mending of liglit and shade. 



4. MouU'i Photogenic Arrangement. Unaware of Mr. 

 Moule's invention, we tried, in 1856, some ex]>urimcuts 

 with a compound called blue fire, composed of the 

 following ingredient* : 



Nitre 4 parts. 



Sulphur 2 



Sulphide of antimony . .1 part. 



And found that a portrait, nearly equal to that obtained 

 by daylight, can be produced. Mr. Moule, we believe, 

 adopts Rome chemical compound similar to that we have 

 named ; but in addition he uses a lamp, in which the 

 substance ia burned. Photographs taken by such 

 means are very good, and well defined as regards half 

 tones, Ac. The process, however, has not been largely 

 employed ; and, so far as we know, has never been used 

 commercially, having been confined chiefly to lect 

 table purposes. 



Ordinary gas, oil, and paraffine lights, have a very 

 slight action on collodionixed platvs ; aud we shall there- 

 fore not enter into details respecting them. 



The electric and oxy-hydrogen lights, but especi- 

 ally the former, are of great value in curtain circum- 

 stances. In many of the museums of this and other 

 countries, there are objects which, from their size, <tc., 

 are necessarily placed in positions where BUfh'ciuut day- 

 light can scarcely impinge on them for the purposes of 

 the photographer. In such cages, the electric light has 

 l>eeu frequently employed with great success; and 

 photographs of many interesting objects liave been ob- 

 tained. As the objections which exist to portraits 

 taken thus, are rather advantageous when the pictures 

 of inanimate articles are required, the electric and oxy- 

 hydrogen lights afford the most eligible means of illumi- 

 nation in such cases. 



CELESTIAL PHOTOGRAPHY. 



OSE of the most surprising achievements of modern 

 science, is that of taking views of the, heavenly bodies ; 

 which, in the cose of the moon, are so accurate, as to 

 permit our tracing the valleys aud mountains repre- 

 sented on photograplis of her surface. The difficulty 

 incident to such attempts, will be better estimated when 

 we compare the perfect stillness required of a person 

 sitting for a likeness, with the circumstances which have 

 to be allowed for in celestial photography. Some of 

 these we may name, in connection with lunar photo- 

 graphy. In the first place, the earth is rotating on 

 its axis, at the rate of 1,000 miles per hour. At the 

 same time, we are travelling through space at a ra[>M 

 rate. The moon, again, is revolving round the earth at 

 the rate of about 2,000 miles pur hour. The difficulty, 

 therefore, at once presents itself, as to how sufficient 

 absence of motion, or its equivalent, can be obtained for a 

 few seconds of time. This is managed by so arranging 

 the telescope, <fcc., by moans of clockwork, as that it 

 shall travel an angular distance equal to that traversed 

 by the heavenly body in any space of time. 



Our readers will understand the principle- of this, if 

 we afford them a familiar illustration. \Ve will .suppose 

 the case of a steam-boat in motion, towards which a 

 telescope is being pointed by an observer on shore. The 

 instrument, if gradually shifted, will apparently present 

 the steamer to the eye at a state of rest ; and the angu'ar 

 motion of the telescope will require to be less, exactly in 

 proportion to the distance of the steam-boat. 



Now the heavenly bodies are in a similar position; 

 and as we know the exact rate of their, and our own, 

 passage through space, it becomes a matter of pure 

 mical arrangement to accommodate the annular 

 n of our in-:nimeiiU to them. This is done by 

 means of clockwork ; and the arrangements lately em- 

 ployed have affonleil -.nine very interesting results. 



The most tecent instances of this application of pho- 

 !iv, is i hat effected during the solar eclipse of 

 July IMth, If 1 10. To those of our rca.lers who are unac- 

 quainted with astronomy, we may explain, that some 



advantage of being oxact liken B*SBS, together with that 

 peculiarly pleasing expression which the taste of a tho- 

 rough artist can alone give. 



W,- li. ( \e frequently employed photography for another 

 purpone, to which we will refer ; and our remark* may be 

 useful to the managers of Mechanics' Institutions, <tc. 

 The ordinary mode of producing dissolving view*, is that 

 of first sketching on glass by mean* of Indian ink, and 

 then of tilling up the outline* with transparent colours. 

 Instead of this plan, we have had portrait* and land- 

 scape* first photographed, and afterward* coloured by 

 the artist. The result is a pleasing and accurate pic- 

 which, when magnified by mean* of the dissolving 

 s or magic lantern, present* an exact illustration of 

 an object on the screen. We have employed magnifying 

 powers vat-vim; from one to sixteen thousand times 

 superficial, and can strongly recommend our plan to all 

 who are desirous of having set* oT views painted. 



Care must be taken that the colours employed are 

 quite transparent ; that the collodion film is not too 

 thick ; and it is also essential that the lenses of the 

 lanterns should be as free a* possible from spherical 

 aberration. The effects of this are avoided by the artist, 

 as he paints all straight lines at a slight curvature : of 

 course this is not allowed for in the photograph, which 

 strictly represents objects as they actually appear. 



PHOTOGRAPHY BY ARTIFICIAL LIGHT. 



THE comparative absence of the chemical or actinic 

 rays in most kinds of artificial light, render them un- 

 suitable for the purposes of photography in many case*. 

 It is, however, possible to obtain pictures by means of 

 the oxy-hydrogen light, the electric light, aud the com- 

 bustion of some substances ; and as there has been but 

 little published on the subject, we shall confine our 

 remarks to our own researches and experiments. 



We have succeeded in taking likenesses by means of 

 the following arrangements : 



1. Thr. Kl'ctnc Ltqht. For this purpose a powerful 

 voltaic battery of fifty cells of Grove's battery was 

 employed, together with a modification of Duhoxcq's 

 electric lamp. The cells were arranged in single series, 

 and each platina exposed an active surface of twenty- 

 eight square inches. The length of flame was about 

 half an inch, and, as nearly as could be judged, about a 

 quarter of an inch thick. No reflector was employed, 

 ami the sitter was placed at about three feet from the 

 charcoal points. Ordinary collodionised plates, which, 

 on an average, required from twenty to fifty seconds' 

 exposure in the camera by daylight, were used ; the mani- 

 pulation, A-c.. being identical with the usual mode pur- 

 sued in daylight photography. 



An equally good photograph was produced by an 

 exposure to the electric light for about thirty to forty 

 second*, so far as the intensity of the light and shade 

 of a positive was concerned. But, strange to say, the 

 same objection exists to such photograplis as is found in 

 the use of the electric light for illuminating purposes 

 namely, that of the excessive depth of light and shadows, 

 all half tones seeming to be entirely lost. 



To remedy this, we trial a variety of arrangements, 

 but entirely without success. The face of the sittcf 

 presented a deadly or ghastly white appearance on the 

 plate ; whilst any shaded or dark part of the dress or 

 skin, was equally black. The picture itself was there- 

 fore divided into two appearances only, and was entirely 

 deficient of pleasing expression. In no trial with a 

 varying strength of the light, did we succeed in temper- 

 ing this excessive contrast of effect. 



2. The Vsy-h-iilro-ten Light. Owing to a less amount 

 of actinic rays in this light, the solarising effect is not 

 so intense. Longer time of exposure is required, ev.-u 

 to the extent of one minute ; depending, of course, on 

 the sensitive nature of the plate. 



3. Thr CiimliMstinn nf Photphonu in Oxygen. By this 

 plan a mrwt intense light is produced ; but owing to its 

 short cotitimi met-, it is of little or no avail. The pic- 

 ture* are, however, softer than those produced by the 



