4'0 THE ESSEX FIELD CLUB. 



to show what enormous strides in the study of nature had been made directly a 

 new weapon had been placed in the hands of scientific workers. The object of 

 the present lecture was to show how the photographic plate had within the 

 knowledge of the present generation become an indispensable adjunct to science. 

 The lecturer said that the first successful photographs on silver salts were taken 

 by Dague: re ^ who began his researches independently, but afterwards entered 

 into partnership with Joseph Nicephore Niepce, of Chalons ; the latter had 

 previously been taking photographs on metal plates coated with bitumen, a 

 method which endures to this day in photo-mechanical work. Fox-Talbot had 

 also been working independently in England with silver salts upon paper, and 

 his process was made public in this countrj' about the same time that Daguerre's 

 method was made known in France, both of which events occurred in 1839. 

 After the publication of the discoveries of Daguerre and Fox-Talbot, the 

 chemical and optical departments of photography became united. The camera 

 obscura \z said to have been invented by Porta in the sixteenth or seventeenth 

 Century, but perhaps it was known to Roger Bacon in the thirteenth century. 



As he intended to speak upon the scientific uses of photography, he would 

 fit-st point out that the camera image, being formed by a lens, is not much limited 

 in size, either in the way of enlargement or reduction. For instance, a lady had 

 just placed in his hands the smallest Johnson's Dictionary in the world ; the 

 reading of it had to be done through a magnifying glass. As the little volume 

 was indirectly issued as an advertisement, he would not push it any further. 

 This reduction by means of photography was largely utilised during the siege of 

 Paris by the establishment of the pigeon post ; documents and newspapers were 

 photographed on a greatly reduced scale upon collodion films, which were then 

 stripped off the glass, placed in quills, and carried attached to the tail feathers 

 of the birds. When the destination was reached, these missives were pro- 

 jected on to a screen and enlarged, by means of the optical lantern, and anything 

 required from them was taken down by shorthand reporters in the room. 



Mr. Meldola said that photography might be used for purposes of fraud, such, 

 for instance, as the representation of ghosts in the so-called " spirit photographs," 

 and he exhibited some pictures on the screen, photographed by one of his students, 

 in vviiich the person acting as ghost had been in position during but a portion 



2 In a report of the lecture published in " Photography," I am credited with the statement that 

 Daguerre was the first to introduce silver salts into photography, and this statement is made the 

 subject of an editorial criticism. The writer of the note has, however, fallen into some error or 

 must have misunderstood my remark. That I was aware that Schulze had previously experi- 

 mented with silver compounds appears from the following extract from my book on "The 

 Chemistry of Photogmphy," which was published in 1889, the lectures forming the subject of 

 the work having been delivered in 1888: — " 'J'he first distinct statement as to the darkening of a 

 silver compound being the result of the influence of light was made by a German physician, J. H. 

 Schulze, who in 1727 observed that when a solution of silver in nitric acid was poured on to chalk 

 the precipitate darkened on the side exposed to light," etc. (p. 36). 



Again, in a Friday evening discourse delivered at the Royal Institution on May i6th, iSpo, I 

 said; — " If the word 'photography' be interpreted literally as writing or inscribing by light, 

 without any refcreftcc to the auhsequcnt pe'manence 0/ the inscription, \\\^n the person who 

 first intentionally caused a design to be imprinted by light upon a photo-sensiiive compound must- 

 be regarded as the first photographer. According to Dr, Eder, of Vienna, we must place this 

 experiment to the credit of Johann Heinrich Schulze, the son of a German tailor, who was born 

 in the Duchy of Magdeburg, in Prussia, in 1687, and who died in 1744, after a life of extra- 

 ordinary activity as a linguist, theologian, physician, and philosopher. In the year 1727, when 

 experimenting on the subject of phosphorescence, .Schulze observed that by pouring nitric acid, in 

 which some silver had previously been dissolved, on to chalk, the undissolved earthy residue had 

 acquired the property of darkening on exposure to light. This effect was shown to be due to 

 light, and not to heat. By pasting words cut out in paper on the side of the bottle containing 

 ihe precipitate, Schulze obtained copies of the letters on the silvered chalk. The German 

 philosopher certainly produced what might be called a temporary photograiii.' Proc. Roy. Inst., 

 vol. xiii., p 134. I have nothing to add to these extracts ; they are amply sufficient to show thai 

 I was acquainted with the work of Schulze — R.M. 



