58 
Dr MacCullocIi on Peat, 
examination. Occasionally? it is dispersed among the more solid 
peat, which consists of powdered materials, fragments and fibres, 
to which it communicates a black colour and pitchy appearance. 
It cannot then be extracted by water, as far as I have experien- 
ced, since, when once hardened, and in a detached state, it is 
not soluble even in boiling water. When first this matter is 
procured, it is soft, but when dried, it is brittle, and breaks with 
a splintery and conchoidal fracture, presenting a considerable 
resemblance to asphaltum. It also sometimes resembles that 
substance in lustre, but is at other times dull, and the colour is 
black. It is heavier than water, and is not electric. It is not 
acted on, as already remarked, by boiling water, nor is it solu- 
ble in alcohol, ether, or naphtha ; in which latter circumstance 
its difference from asphaltum, which it othermse so much re- 
sembles, is strongly marked. On distillation, it gives the same 
results as ordinary peat, namely, acetic acid and vegetable tar, 
the charcoal remaining behind. These results prove, that, like 
undecomposed vegetables and peat, it contains oxygen as well 
as hydrogen and carbon. The quantity procured for the exjpe- 
riments in question, was too small to show whether any azote 
exists together with the other elements, as no ammonia was 
found in the small proportion of acid obtained. 
It has not, as far as I know, been observed by our numerous 
writers on this subject, that peat is occasionally luminous, al- 
though a remark of an analogous nature is made by some orien- 
tal traveller, whose name does not at this moment occur. I 
have often, however, witnessed this appearance, and most re- 
mairkably in the bared bogs of North and South Uist. The 
luminous matter is dispersed in small points over the brown 
surface, and as these are very minute, while the colour of the 
light is also blue, they are scarcely visible at a small distance, 
whence, probably, they have escaped notice. This fact is ana- 
logous to that which occurs during the decomposition of wood ; 
but the present state of chemical analysis does not appear to 
offer any means of ascertaining the ca,use of the phosphorescence. 
The specific gravity of peat varies considerably, and, in a 
great measure, in proportion to the degree of its perfection ; in 
a few instances it is found to sink in water. Its qualities as a 
fuel depend much on its varying condilion in this respect ; that 
