ON THE COLOUR OF THE BLOOD. 125 1 



for the consideration of this learned Society, my observations 

 and arguments in favour of a new theory, predicated on the 

 Newtonian and pneumatic philosophy, in explaining the sub- 

 jects of this Essay. 



From the experiments which I have made on light, and from 

 those detailed by the great Newton and other celebrated philoso- 

 phers, on which we may rely, it appears, that light is a mixture of 

 seven different coloured rays, of different refrangibilities and re- 

 flexibilities, and that we are indebted to the sun for all the light 

 we enjoy; that heat is a simple elementary body, and a necessary 

 constituent of this planet ; that oxigene gas is a compound of 

 light, heat, and oxigene, and that oxigene is held in its gaseous 

 state by the means of caloric; all of which have been proved 

 by numerous experiments made by Bcrthollet, Davy*, and 

 other eminent chemists, which being conceded, renders it un- 

 necessary to detail them here.— -It has also been proved beyond 

 the possibility of doubt, by the experiments of the most re- 

 spectable chemists, that the blood contains iron. — Hence when 

 atmospheric air is taken into the lungs, the oxigene gas is ab- 

 sorbed by the blood in its passage through the lungs during 

 respiration, and from the great affinity of oxigene to the iron 

 in the blood, it unites with that metal, and the red ray, a con- 

 stituent of oxigene gas (the most difficult of rcfrangibility) is 

 absorbed at the same time by the iron and becomes fixed, which 

 constitutes the red oxide of iron, and illustrates in a philoso- 

 phical manner, the beautiful phenomenon of the vermilion co- 

 lour of the blood; while the heat is set at liberty, and the other 

 six constituent rays of light, either become fixed in the other 

 parts of the blood, or are carried off in a latent state, by expi- 

 ration; for it is an established principle in optics, "that some rays 

 enter into the combination of bodies, while others are reflected, 

 and this in proportion to the greater or less affinity of the se- 

 veral rays with these bodies." 



According to the experiments of Mr. Davy, on the com- 

 position of the nitrous oxide gas, and its comparative influence 



• With the exception that Mr. Davy make6 to the existence of cahric altogether. — The first 

 evidence of the existence of matter, is that, it has motion, all the eiperimenti on heat, prove its 

 ■lOBicinuni, and consequently it has attached to it all the propti tiii of matter. 



