and its application to taking Portraits from the Life. 223 



sufficient to characterize it, as well as to show each button, 

 button-hole, and every fold. 



Partly owing to the intensity of such light, which cannot 

 be endured without a distortion of the features, but chiefly 

 owing to the circumstance that the rays descend at too great 

 an angle, such pictures have the disadvantage of not exhibit- 

 ing the eyes with distinctness, the shadow from the eyebrows 

 and forehead encroaching on them. 



To procure fine proofs, the best position is to have the line 

 joining the head of the sitter and the camera so arranged as 

 to make an angle with the incident rays of less than ten de- 

 grees, so that all the space beneath the eyebrows shall be il- 

 luminated, and a slight shadow cast from the nose. This in- 

 volves obviously the use of reflecting mirrors to direct the 

 ray. A single mirror would answer, and would economise 

 time, but in practice it is often convenient to employ two ; one 

 placed, with a suitable mechanism, to direct the rays in ver- 

 tical lines ; and the second above it, to direct them in an inva- 

 riable course towards the sitter. 



On a bright day, and with a sensitive plate, portraits can 

 be obtained in the course of five or seven minutes, in the dif- 

 fused daylight. The advantages, however, which might be 

 supposed to accrue from the features being more composed, 

 and of a more natural aspect, are more than counterbalanced 

 by the difficulty of retaining them so long in one constant 

 mode of expression. 



But in the reflected sunshine, the eye cannot support the 

 effulgence of the rays. It is therefore absolutely necessary 

 to pass them through some blue medium, which shall abstract 

 from them their heat, and take away their offensive brilliancy. 

 I have used for this purpose blue glass, and also ammoniaco- 

 sulphate of copper, contained in a large trough of plate glass, 

 the interstice being about an inch thick, and the fluid diluted 

 to such a point, as to permit the eye to bear the light, and 

 yet to intercept no more than was necessary. It is not re- 

 quisite, when coloured glass is employed, to make use of a 

 large surface ; for if the camera operation be carried on until 

 the proof almost solarizes, no traces can be seen in the por- 

 trait of its edges and boundaries; but if the process is stopped 

 at an earlier interval, there will commonly be found a stain, 

 corresponding to the figure of the glass. 



The camera I have used, though much better ones might 

 be constructed, has for its objective two double convex lenses, 

 the united focus of which for parallel rays is only eight inches ; 

 they are four inches in diameter in the clear, and are mounted 

 in a barrel, in front of which the aperture is narrowed down 

 to 3j inches, after the manner of Daguerre's. 



