Art of Fhotogenic Dratsoing. 205 



purpose of seeing that the ground is eveii. If it appears so 

 when thus tried to a small extent, it will generally be found to 

 prove so in the final result. But if there are some places or 

 spots in it which do not acquire the same tint as the rest, such 

 a sheet of paper should be rejected : for there is a risk that, 

 when employed, instead of presenting a ground uniformly 

 dark, which is essential to the beauty of the drawing, it will 

 have large white spots, places altogether insensible to the 

 effect of light. This singular circumstance I shall revert to 

 elsewhere : it is sufficient to mention it here. 



The paper then, which is thus readily sensitive to the light 

 of a common window, is of course much more so to the direct 

 sunshine. Indeed, such is the velocity of the effect then pro- 

 duced, that the picture may be said to be ended almost as 

 soon as it is bearun. 



To give some more definite idea of the rapidity of the pro- 

 cess, I will state, that after various trials the nearest evaluation 

 which I could make of the time necessary for obtaining the 

 picture of an object, so as to have pretty distinct outlines, 

 when I employed the full sunshine, was half a secofid. 



§ 9. Architecture, Landscape, and external Nature. 



But perhaps the most curious application of this art is the 

 one I am now about to relate. At least it is that which has 

 appeared the most surprising to those who have examined my 

 collection of pictures formed by solar light. 



Every one is acquainted with the beautiful effects which are 

 produced by a camera obscura and has admired the vivid pic- 

 ture of external nature which it displays. It had often oc- 

 curred to me, that if it were possible to retain upon the paper 

 the lovely scene which thus illuminates it for a moment, or if 

 we could but fix the outline of it, the lights and shadows, di- 

 vested of all colour, such a result could not fail to be most in- 

 teresting. And however much I might be disposed at first to 

 treat this notion as a scientific dream, yet when I had suc- 

 ceeded in fixing the images of the solar microscope by means 

 of a peculiarly sensitive paper, there appeared no longer any 

 doubt that an analogous process would succeed in copying the 

 objects of external nature, although indeed they are much less 

 illuminated. 



Not having with me in the country a camera obscura of any 

 considerable size, I constructed one out of a large box, the 

 image being thrown upon one end of it by a good object glass 

 fixed in the opposite end. This apparatus being armed with 

 a sensitive paper, was taken out in a summer afternoon and 

 placed about one hundred yards from a building favourably 



