42 
According to Mr. Hunt, others who have had a lengthy experience in electric 
blasting, enumerate its advantages over ordinary fuse-blasting thus:—• 
1. It economizes capital, time, and explosive material; 2. It is more certain; d. It is more 
effective; obstacles are overcome which cannot be removed by the ordinary system of blasting; and 4. It 
is safer, inasmuch as absoluto protection to life is secured. The essential points (adds Mr. Hunt) to be 
observed in electric blasting operations are to have a reliable fuse, a machine capable of giving a strong 
electric spark, good conducting cables, and insulated connecting wires, so as to ensure the passage of the 
spark to the fuses included within the electric circuit.A series of shot holes charged 
with dynamite maybe simultaneously fired by means of u high ” or “ low ” tension electricity. High 
tension electricity is obtained by a frictional or dynamo-electric machine; low tension electricity by a 
galvanic battery or low tension exploder. In employing high tension electricity, it is necessary that the 
leading or positive wire should be well insulated, otherwise a serious leakage of the electric charge is apt lo 
occur, especially if the wire should happeu to bo in contact with the earth, or with any conducting material. 
For the conveyance of low tension electricity, the insulation of the leading or positive wire need not bo perfect; 
but the copper forming this wire should bo of comparatively large section. In the use of high-tension elec¬ 
tricity, the line resistance upon the current is but small; consequently, with a well-insulated wire, most 
of the electricity produced may be conveyed to fuses placed at considerable distance from the firing machine. 
On the other band, the line resistance to low-tension electricity is so great as to render it desirable to 
make the distance between the firing machines and the fuses as short as possible. 
On the subject of shot-firing in mines, a circular has been issued from the Home 
Secretary’s Office to all colliery proprietors in the United Kingdom, in which it is 
stated to he the intention of the Government to make it compulsory that a specified 
time shall be set apart daily for firing shots, and that only such persons as are actually 
engaged in firing shall he allowed in the collieries during that time. It would be well 
if a similar rule were adopted in all the mines of this colony. 
BOILERS. 
On this subject, Mr. E. R. Meekison, the Travelling Inspector of Mines and 
Machinery, has forwarded to me the following report:— 
The boilers used in mining are mostly of the Cornish flue typo, with the fire in the tube, and the 
pressure used in the great majority of cases is 40 lbs. per square iucli. 
One of the great items of expense in mining is firewood, and a great saving in the consumption of 
fuel could be effected (where the feed water is good) by adopting the multitubular boiler, and working the 
steam expansively, with a much greater pressure on the boiler than is now used. The engines that have 
not expansive gear could have it put on at a moderate expense, and the saving could still further bo 
increased by using compound engines, the difference in cost of the machinery being soon mado up by the 
saving effected in firewood. 
The majority of boilers at present in use aro not adapted for a much higher pressure than 40 lbs. 
per square inch, as mining companies, when purchasing boilers by tender, very often take the lowest offer, 
irrespective of the class of iron or workimiuship, but they would find it true economy to pay a good price 
for the best material and workmanship, and so avoid much of the loss caused by stoppages for repairs. 
All the boilers used for mining (without any exception known to me) have been tested by hydraulic 
pressure to not less than 50 per cent, over the working pressure within the last twelve months. In cases 
where mining managers bad not allowed this margin of safety, I have asked them to re-test the boilors, and 
they have always complied by doing so on as early a date as possible. In cases where I considered the 
mountings defective, or any necessary appliances wanting, on drawing attention to them, the defects have 
been acknowledged and remedied, and in all my inspections I have not met with a refusal to comply with 
my requests. 
I would suggest it be mado compulsory to test boilers to not less than one ami a half the working 
pressure. I would also suggest that, from as early a date as possible, it should be made compulsory that 
all boilers, either new or secondhand, should he inspected inside and outside, and tested to not less than one 
and a half, the proposed working pressure, before being erected and built in position, and that a certificate 
be given, classing the boilers as 1st, 2nd, or 3rd class, and stating to what pressure tested, and also the 
allowed working pressure taken from the test; any boiler users working with a higher pressure than 
certified to be prosecuted. 
I have, within the last six years, inspected for companies several boilers that I did not consider fit to 
be worked again, and have reported so, but I have know r n such boilers to be sold afterwards at a low rate to 
other companies. Machinery merchants often tender to supply and erect plants on a purchasing lease, 
mining companies paying a deposit of about £50 and a weekly rental, such rental going towards the purchase- 
money. Inferior boilers which are never examined by any engineer, and which no company would take 
if they had to pay cash for them, are often supplied on these conditions, but by making the examination 
and testing compulsory, it would prevent unfit boilers being erected in the future. If this suggestion is 
adopted, I think it should be part of ray duty to examine and test all boilers and complete plants before 
they are started to work. 
I would further suggest that boilermakers or importers, when selling now boilers, should be 
required to give a certificate, stating date of sale, what brand of iron, thickness of material, and all 
particulars of construction of such boiler. If the boiler were re-sold after having been used, the certificate 
