MOONLIGHT, ARTIFICIAL LIGHT, AND DRUMMOND'S LIGHT, ARE ALL ACTIVE. 



type, beyond that which arises from her motion. By the aid of a lens and a heli- 

 ostat, I caused the moonbeams to converge on a plate, the lens being three inches in 

 diameter. In half an hour a very strong impression was obtained. With another 

 arrangement of lenses I obtained a stain nearly an inch in diameter, and of the general 

 figure of the moon, in which the places of the dark spots might be indistinctly traced. 



546. An iodized plate, being exposed for fifteen seconds only close to the flame of a 

 gas light, was very distinctly stained; in one minute there was a very strong impression. 



547. On receiving the image of a gas light, which was eight feet distant, in the ca- 

 mera, for half an hour, a good representation was obtained. 



545. The flame of a gas lamp was arranged within a magic lantern, and a portion 

 of the image of a grotesque on one of the slides received on a plate ; a very good 

 representation was procured. 



549. With DRUSIMOND'S light, and the rays from a lime-pea m the oxy-hydrogen 

 blowpipe, the same results were obtained. 



550. In the first experiments which I made for obtaining portraits from the life, 

 the face of the sitter was dusted with a white powder, under an idea that otherwise 

 no impression could be obtained. A very few trials showed the error of this ; for 

 even when the sun was only dimly shining, there was no difiicultv in delineating the 

 features. 



551. When the sun, the sitter, and the camera are situated in the same vertical 

 plane, if a double convex non-achromatic lens of four inches diameter and fourteen 

 inches focus be employed, perfect miniatures can be procured, in the open air, in a 

 period varying w r ith the character of the light, from 20 to 90 seconds. The dress, also, 

 is admirably given, even if it should be black ; the slight differences of illumination are 

 sufficient to characterize it, as well as to show each button, button hole, and every 

 fold. 



552. 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 de- 

 scend at too great an angle, such pictures have the disadvantage of not exhibiting the 

 eyes with distinctness, the shadow from the eyebrows and forehead encroaching on them. 



553. 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 degrees, so that all the space beneath the eyebrows shall be illuminated, 

 and a slight shadow cast from the nose. This involves obviously the use of reflecting 

 mirrors to direct the ray. A single mirror would answer, and would economize time, 

 but in practice it is often convenient to employ two : one placed, with a suitable mech- 

 anism, to direct the rays in vertical lines ; and the second above it, to direct them in 

 an invariable course towards the sitter. 



554. On a bright day, and with a sensitive plate, portraits can be obtained in the 

 course of five or seven minutes in the diffused 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. 



