Tetramorphism of Carbon. 151 



that it is much more probable that they really are of those values, 

 though the nature of the case prevents me from being so sure as 

 when tangible crystals can be measured by the reflecting goniometer. 

 These angles will at once be seen to be such as are derivable in the 

 simplest manner from the regular system ; and the way in which 

 they are associated fully agrees with that supposition. 



In a similar manner I find that anthracite is crystallized in the 

 square prismatic system, the axes having the relative values of 5, 6, 

 and 3. It cleaves nmch more readily than coke, and many more 

 good angles can be found than in it. It is, however, very much 

 more complicated in its structure, for not only does it cleave with 

 relation to the axes 5, 5, and 3, but also to four times the axis 3 ; 

 and owing to this property so great a number of angles are found as 

 to make it somewhat confusing. The anthracite, which I have chiefly 

 used in my experiments, is a very good specimen of American, and 

 it cleaves best through the extremities of the axes 5, 6, and 3, though 

 also with relation to four times 3, as can frequently be seen from 

 the same fragment. Some other specimens which I have examined 

 appear to cleave more readily in the latter direction. To explain 

 the manner of derivation of the various angles which occur would 

 occupy more space than it would deserve. I shall, therefore, merely 

 give their approximate values, and content myself with stating that, 

 both in magnitude and arrangement, they are all readily derivable by 

 various most simple cleavages from a square prism having its axes of 

 the relative values of 5, 6, and 3. To show how closely most careful 

 measurements agree with this supposition, I will give two examples, — 

 observations 99° 24', also 106° IV ; theory 99° 22', and 106° 25'. 



The following are among the most common angles which occur, 

 80i°,99i°, 40i°, 49f°, 90°, 45°, 52f°, 74^°, 62°, 118°, 31°, 69°, 

 which are related to the axes 5, 5, and 3 ; also 22^°, 67 i°, 16^°, 

 73^°, which are related to the axes 5, 5, and four times 3. We 

 have by various intersections others, but it is needless to particu- 

 larise them. 



Although charcoal, from its nature, is ill fitted for such an exami- 

 nation, yet, by proceeding in the manner above described, I have 

 found in it angles which agree with those of anthracite as closely as 

 could be measured, but only in particles of about to,^I)o^^^ of an 

 inch in diameter. Lamp-black presents merely a granular appear- 

 ance, as though consisting of clusters of particles of about x^ohyoothi 

 of an inch in diameter, and no trace of crystals. The same may be 

 said of gas carbon which, however, is chiefly of the coke form, as is 

 shewn by its specific gravity and metallic lustre. 



"Whence it should appear that we have carbon crystallized in three 

 different systems — the regular, rhombohedric, and the square pris- 

 matic ; and what is remarkable, it occurs in two distinct conditions 

 with different volumes and properties in the same system, the regular, 



