Mr. Watt’s Observations 
280 
of amorphous basalt, here called Rowley Rag, was broken into 
small pieces, and deposited gradually on the elevated part of the 
interior of the furnace, between the fire and the chimney, from 
whence, as it melted, it flowed into the deeper part, in which, in 
ordinary operations, the melted iron is collected. It was observed 
by the persons attending, that it did not require half the quan- 
tity of fuel, to fuse the basalt, that would have been necessary 
to melt ah equal weight of pig iron. When the whole was 
melted, it formed a liquid glass,, rather tenacious, from which a 
large ladle-full was taken, which, on being allowed to cool, 
retained the characters of perfect glass. The fire was main- 
tained, though with gradual diminution, for more than six hours ; 
after which time, the draught of the chimney was intercepted, 
the surface of the glass was covered with heated sand, and the 
furnace was filled with coals, which were consumed very slowly. 
It was eight days before the mass in the furnace was sufficiently 
cool to be extracted, and even then it retained considerable 
internal heat. 
The form of the mass, being given by the bottom of the 
furnace, was considerably irregular, approaching to the shape 
of a wedge whose lower angles were rounded. It was nearly 
three feet and a half long, two feet and a half wide, about four 
inches thick at one end, and above eighteen inches at the other. 
From this diversity of thickness, and from the unequal action of 
the heat of the furnace, too great an irregularity had prevailed in 
the refrigeration of the glass, to permit its attainment of a ho- 
mogeneous texture. These circumstances might probably have 
been counteracted by better devised precautions ; but the ine- 
quality of the product is not to be regretted, since it has for- 
tuitously disclosed some very singular peculiarities, in the 
