LIGHT-PAIMING. 29 



limitation or divisibility, that is to say, at least two or three of the cate- 

 gories of Kant. In so far as the reason is in possession of all these 

 ideas, it is here already knowing (in the possession of knowledge ;) the 

 ^'■Doctrine of knowledge'''' [ WiHsenschaftslehre,] as Fichte called his 

 philosophy, thus in part pre-supposes knowledge, but does not give it 

 in its whole extent. 



Jn the second place, this whole deduction supposes not only certain 

 ideas, but still more a fact, the fact of consciousness, and accords, by im- 

 plication, to that fact the authority of a first fact which renders all the 

 rest possible. It is, therefore, in the last analysis, this fact which is the 

 principle sought for. In other words, the principle is no other than the 

 principle of all psychology, or the principle of Descartes. So much 

 ado was not necessary for such a discovery. 



All the novelty is in the rigorously abstract, or, to speak correctly, 

 algebraic form given to the exposition of the fact. This form has its 

 value ; it may be useful to constitute the science as an abstract science; 

 it may even serve for the discovery of some ulterior developments. — 

 But, at the bottom, science has, in all this, made no progress, and the 

 critical philosophy has not filled up any of its gaps. Fichte only ex- 

 plains what Kant implies. 



LIGHT-PAINTING. 



The last quarter of a century seems to stand pre-eminent for the dis- 

 coveries in Physical Science, and their numerous practical applications 

 to the ornamental and useful purposes of life, which have been made 

 during that period. The impondcrahles^ heat, light, and electiicity being 

 in consequence of their intangibility, but imperfectly known as to their 

 more recondite properties and laws, have afforded the richest acquisi- 

 tions. Among these may be enumerated Plwtography^ or the process 

 of making drawings and taking copies of natural and artificial objects 

 by the agency of light. 



It has been, for some time, known that light exerted an important in- 

 fluence in producing chemical changes in many metallic compounds, in 

 virtue of which their color was either deepened or discharged. Thus 

 the nitrate and chloride of silver were known to be blackened when ex- 

 posed to the light of the sun. The nitrate has, for a long time, been 

 used as the basis of indelible ink for marking linen ; the writing being 

 immediately exposed to a strong light or the heat of a warm flat-iron^ 

 during which exposure it became intensely black. Early in this centu- 

 ry, Wedgewood and Davy obtained tolerably correct copies of objects 



