621 
The preceding results give an approximate idea of what 
may be expected from the steam jet under similar circum- 
stances. In adapting the principle to the entire ventilation of 
a colliery of considerable extent, it would be found necessary 
to employ several such annular jets as the one described. 
It should, however, be borne in mind that in carrying out 
the plan on a large scale, a more suitable and convenient 
arrangement might be adopted. For example, the jets may 
be applied directly over the upcast shaft, and instead of 
using several small jets, one only, of suitable area and 
enlarged circumference, may be used. Such an arrangement 
would no doubt answer well, and may possibly be adopted 
with advantage under particular circumstances, but the 
consumption of fuel and expense of boilers would be great 
in proportion to the amount of ventilation produced. 
ON THE VENTILATION OF MINES. BY MR. J. JEBSON, 
MINING ENGINEER, MOLD GREEN, NEAR HUDDERSFIELD. 
This is a subject which has excited almost universal atten- 
tion, and its importance demands the most earnest and patient 
study on the part of all who are interested in the matter ; 
and though it has been investigated and much improved by 
the learned and most eminent men in science as well as 
practice, yet there is room for further progress ; and where 
human life is endangered, there skill and science ought to 
co-operate, and be brought to bear to ensure safety. The 
perseverance and industry already bestowed on this all- 
important subject has not been in vain, as would be more 
clearly seen if we were to compare the present state of 
ventilation in mines, and the mode of working in general, 
with what it was twenty, nay, even ten, years ago ; not that 
