298 Considerations on Colours, &fc. 



rene towards the part corresponding 1o the sun, and if there 

 be over our heads any of those Hght clouds which are ex- 

 ceedingly high, thev will be seen at a later period clothed 

 with a brilliant red, heightened bv the dinnnution of the 

 light on the earth, soon after darkened, and at length ex- 

 tinguished in the shade. 



COXCLVSION. 



Notwithstanding the many fine discoveries already made 

 in regard to light, the thcorv of the production of colours 

 has not vet acquired that generality which renders it appli- 

 cable to all ca>es, and to that simplicity of principles to 

 which we arc always conducted when we discover the real 

 laws of nature. Many phaenomena have never been ex- 

 plained ; and tl"te explanation given to several necessarily 

 requiies to be rectified. The author proposes to establish 

 changes in theory, the want of which he points out. He 

 founds his rtasoiiing partly on the doctrine and facts gene- 

 rallvadnntted, and partly on other information less diffused, 

 though lone; known, and on his own observations. But he 

 is far from flattering himaeif with the idea of having pre- 

 sented these objects properly in a sketch such as this me- 

 inoir. He even was soon sensible that a subject so exten- 

 sive and complex would require more time and labour. 



To fill up many vacuities, to develop several points, and 

 to rectiiV and extend others bv researches, new experi- 

 ments, and profound reflection, — such is the ample task of 

 improvement. If his health and occupations permit, he. 

 will endeavour to undertake it. 



It would he of utility, and also just, to give at the same 

 time a short account of what we are indebted to the great 

 Newton, who opened this career in so admirable a manner, 

 and to the philosophers who have discovered new points, 

 and removed diiBcullics. Greater precision ought also to 

 be employed in the language relating to colours, proportioned 

 to the increase of our knowledge, and the present state of 

 science and the arts. In a word, it would not be too much, 

 in such a branch of science, to add the resources of calcula- 

 tion and geometry to all the riches of experience, and, 'f 

 posc-ibie, to the advantages of the best method. 



XLIV. Oh 



