619 
sumption of steam, it is, nevertheless, found to be very 
useful at times, and is always employed in the morning 
before the men descend the shaft, for giving a good brush 
through. 
It will be observed that the additional parts required in 
the application of the jet in this, as in the preceding instance, 
are very simple, and that the apparatus can be used or not 
at pleasure, by simply reversing the dampers, and opening 
or shutting the steam tap as may be required. 
The effect produced by the chimney itself is pretty good, 
considering, but on opening the damper, while the jet is in 
operation, it presents a striking proof of superior draught — 
the smoke and soot are quickly drawn from the former, and 
thrown out of the iron pipe with the steam. The results 
obtained in this case, however, were not at all in accordance 
with the expectations raised by the apparent success of the 
former application. The leaky condition of the wooden 
pipes and other defects were certainly unfavourable, but 
even with ample allowance for these imperfections, the 
volume of air drawn through the circuitous course of the 
mine was by no means satisfactory in comparison with the 
quantity of steam expended on the jet. 
A number of experiments were therefore commenced with 
a view of forming an approximate idea of the value 
of this plan of ventilation, as compared with others 
more generally adopted, and the results were most 
decidedly in favour of the latter; indeed the expenditure 
of steam was at once found to be so disproportionate with 
the useful effect, that there appeared little inducement 
for further inquiry. 
The following is a brief summary of some of the results 
obtained, with three different jets, viz., a common round jet 
of 4-10ths of an inch area, and two annular jets, one of 
an inch and a half diameter, and the other of two inches 
