230 



KOTES AND QUERIES. 



[No. 255. 



tentive^^ &c. But even this seems, meo guidem 

 judicio, to fall far short of the meaning of the 

 text. Tempera is employed absolutely for tem- 

 pera animum, or tempera tibi, i. e. moderate your 

 feelings, restrain yourself, be calm : three dis- 

 tinct actions in three distinct members, viz. "Take 

 thy pen, and be composed, and write hastily." 



C. H. (1) 



Surely there must be a misprint (twice over) in 

 the communication of your correspondent Ru- 

 PicASTKENSis, unlcss, indeed, he uses a language 

 peculiar to himself. In which case he should have 

 explained his meaning, otherwise to the uninitiated 

 he seems to be poking fun at us with his " quill," 

 when he gravely proposes as an emendation, 

 *' Take thy pen and write quill" J. Eastwood. 

 Cambridge. 



PHOTOGEAPHIC CORRESPONDENCE. 



Specification of the Cdlotype Photographic Process, in- 

 vented by H. r. Talbot, Esq., as enrolled in the Year 

 1841. 



" The first part of my invention is a method of making 

 paper extremely sensitive to the rays of light. For this 

 purpose I select the best writing-paper, having a smooth 

 surface, and a close and even texture. 



" First Part of the Preparation of the Paper. — I dis- 

 solve one hundred grains of crj'staliised nitrate of silver 

 in six ounces of distilled water. I wash one side of the 

 paper with this solution with a soft camel-hair brush, and 

 place a mark upon that side by which to know it again. 

 I dry the paper cautiously at a distant fire, or else I leave 

 it to dry spontaneously in a dark place. Next I dip the 

 paper in a solution of iodide of potassium, containing five 

 hundred grains of that salt dissolved in one pint of water. 

 I leave the paper a minute or two in this solution. I then 

 take it out and dip it in water. I then dry it lightly with 

 blotting-paper, and finish drying it at a fire, or else I 

 leave it to dry spontaneously. AH this process is best 

 done in the evening by candlelight. The paper thus far 

 prepared may be called for the sake of distinction iodized 

 paper. This iodized paper is scarcely sensitive to light, 

 but nevertheless it should be kept in a portfolio, or some 

 dark place, till wanted for use. It does not spoil by keep- 

 ing any length of time, provided it is kept in a portfolio, 

 and not exposed to the light. 



" Second Part of the Preparation of the Paper. — This 

 second part is best deferred until the paper is wanted for 

 use. When that time is arrived, I take a sheet of the 

 iodized paper and Avash it with a liquid prepared in the 

 following manner : dissolve one hundred grains of crys- 

 tallised nitrate of silver in two ounces of distilled water ; 

 to this solution add one-sixth of its volume of strong 

 acetic acid ; let this mixture be called a. Dissolve crys- 

 tallised gallic acid in distilled water as much as it will 

 dissolve (which is a very small quantity) : let this so- 

 lution be called b. When you wish to prepare a sheet of 

 paper for use, mix together t|ie liquids a and b in equal 

 volumes ; this mixture I shall call by the name of gallo- 

 nitrate of silver. Let no more be mixed than is intended 

 to be used at one time, because the mixture will not keep 

 good for a long period. Then take a sheet of iodized 

 paper and wash it over with this gallo -nitrate of silver 

 with a soft camel-hair brush, taking care to wash it on 



the side which has been previously marked. This opera- 

 tion should be performed by candlelight. Let the paper 

 rest half a minute, and then dip it into water, then dry it 

 lightly with blotting-paper ; and lastly, dry it cautiously 

 at a fire, holding it at a considerable distance therefrom. 

 When dry, the paper is fit for use, but it is advisable t« 

 use it within a few hours after its preparation. (^Note. — 

 That if it be used immediately the last drying may be 

 dispensed with, and the paper maj' be used moist.) 

 (Note the second. — Instead of using a solution of gallic 

 acid for the liquid b, the tincture of galls diluted with 

 water may be used, but it is not so advisable.) 



" Use of the Paper. — The paper thus prepared, and 

 which I name * calotype paper,' is placed in a camera ob- 

 scura, so as to receive the image formed in the focus of 

 the lens : of course the paper must be screened or de- 

 fended from the light during the time it is being put into 

 the camera. When the camera is properly pointed at the 

 object this screen is withdrawn, or a pair of internal 

 folding doors are opened, so as to expose the paper for the 

 reception of the image. If the object is very bright, or 

 the time employed is sufficiently long, a sensible image is 

 perceived upon the paper when it is withdrawn from the 

 camera; but when the time is short, or the objects dim, 

 no image whatever is visible upon the paper, which 

 appears entirely blank ; nevertheless it is impressed with 

 an invisible image, and I have discovered the means of 

 causing this image to become visible. This is performed 

 as follows : I take some gallo-nitrate of silver prepared in 

 the manner before directed, and with this liquid I wash 

 the paper all over with a soft camel-hair brush, I then 

 hold it before a gentle fire, and in a short time (varying 

 from a few seconds to a minute or two) the image begins 

 to appear upon the paper. Those parts of the paper upon 

 which the light has acted the most strongly, become 

 brown or black, while those parts on which the light has 

 not acted, remain white. The image continues to 

 strengthen, and grow more and more visible during some 

 time. When it appears strong enough the operation 

 should be terminated, and the picture fixed. 



" The Firing Process. — In order to fix the picture thus 

 obtained, I first dip it into water; I then partly dry it 

 with blotting-paper, and then wash it with a solution of 

 bromide of potassium, containing one hundred grains of 

 that salt dissolved in eight or ten ounces of water ; the 

 picture is then washed with water, and then finally dried. 

 Instead of bromide of potassium, a strong solution of 

 common salt may be used, but it is less advisable. The 

 picture thus obtained will have its lights and shades 

 reversed with respect to the natural objects, videlicet, the 

 lights of the objects are represented by shades, and vice 

 versa. But it is easy from this picture to obtain another, 

 which shall be conformable to nature, videlicet, in which 

 the lights shall be represented by lights, and the shades 

 by shades. It is only necessary for this purpose to take 

 a second sheet of sensitive calotj^pe paper, and place it in 

 close contact with the first upon which the picture has 

 been formed, a board is put beneath them, and a sheet of 

 glass above, and the whole is pressed into close contact 

 by screws ; being then placed in sunshine or daylight for 

 a short time, an image or copy is formed upon the second 

 sheet of paper : this image or copy is often invisible at 

 first, but the image may be made to appear in the same 

 way that has been already stated. But I do not recom- 

 mend that the copy should be taken on calotype paper ; 

 on the contrary, I would advise that it should be taken 

 on common photographic paper. This paper is made by 

 washing good writing-paper, first with a Aveak solution of 

 common salt, and next with a solution of nitrate of silver. 

 Since it is well known, having been freely communicated 

 to the public by myself in the year 1839, and that it 



