The Worlt of the Year. 5 



sun was shown to be a solid or liquid photosphere, bathed in 

 an enveloping atmosphere containing iron, sodium, potassium, 

 lithium, and other metals, in a state of permanent sublimation. 

 Discovery, through the aid of the prism, will not stop here. 

 Science promises that we shall soon know why the planet Venus 

 is so pre-eminently lustrous, like a burnished silver mirror; 

 why Mars has upon his homely visage the hue of a subdued 

 fire; why Saturn looks so cold, and Uranus so peculiarly 

 metallic. The mysteries of the spectrum conduct us beyond 

 the boundaries of the solar system, and offer means of ana-, 

 lyzing the constitution of the stellar masses ; so that Procyon 

 and Syrius, " red Orion, and Arcturus huge/' may severally 

 be made to describe, in the rays of light they flash on us 

 from afar, the nature of their elementary structure, and their 

 chemical relations to the earth we inhabit. Scarcely second. 

 in importance, perhaps practically of greater value, is the 

 method of analysis by diffusion, on which the Master of the 

 Mint communicated a paper to the Eoyal Society on, the 6th, 

 of June last. 



For the purpose of propounding this method, Professor- 

 Graham divides bodies into two classes, — crystalloids, those 

 which exhibit a tendency to crystallize, and which are of 

 high diffusibility ; and colloids, which are of low diffusibility,, 

 affect a vitreous structure, and have little effect on the volatility 

 of the solvent. Examples of crystalloids will occur to the mind 

 of the reader in plenty, and it may therefore suffice to state 

 that animal gelatine is the type of the colloids. The peculiar 

 fitness of gelatine and cognate organic compounds for the pur-, 

 poses of animal organization arise from their plastic nature, and 

 the facility with which they become media for liquid diffusion 

 while still retaining their identity. Passing by the suggestion 

 thus offered us, of new modes of investigating the chemistry of 

 life, we will be content here to indicate the process by which 

 the analysis by diffusion is conducted. A septum of membrane 

 is provided, it may be a sheet of gutta-percha paper, or vege- 

 table parchment, eight or ten inches in diameter, by three inches 

 in depth, formed on a hoop, in the fashion of a sieve. A mixed 

 solution, which may be supposed to contain sugar and gum, is 

 placed upon the septum to a depth of half an inch, and the 

 instrument is floated upon a considerable quantity of water. 

 In the course of time, the sugar — a crystalloid — by its high 

 diffusibility, separates from the gum, leaving the gum in an 

 undiffused state remaining on the septum. In another experi- 

 ment, defibrinated blood charged with a few millegrammes of 

 arsenious acid was found to impart the greater part of the 

 arsenious acid, to the water in the course of twenty-four hours. 

 The diffusate was so free from organic matter, that the metal 



