Electric Lighting Progress in London.
Mr. Frank Bailey’s paper, read at the Society of Arts last Wednesday evening, is a valuable addition to the statistical literature of electric lighting in the metropolis. While it is comparatively an easy matter to describe the details of plant and mains, etc., of the different companies, it is quite another thing to keep carefully tabulated records of points of vital interest to supply companies, and to place them in such a form as to be useful for future reference. Tables of results cover a small area in print, but they are the digest from every day data only to be obtained in the practical working of a large supply company. Thus, a table was given of the life and nature of fracture of a large number of incandescent lamps, all of 25-candle power, from which it apjiears that, out of 536 lamps renewed w’hich were used at a pressure 0/151 volts, the average life of each lam]) was 861 hours, while that of an average of 2549 lamps worked at 120 volts was 923. and of 588 at 99 volts it was 1423 hours; the nature of the failure is then divided under the two headings of “glass globe ” and “ filament fractured,” and these two headings are again subdivided into four or five classes each. It was customary to stamp on the plaster of eadP lamp the date when it was first put into use, with a movable india-rubber stamp, and when it failed it was handed to a storekeeper, who recorded the date and tabulated the results. We believe that if as much trouble were taken by electric light companies to obtain accurate and trustworthy data, as has been taken by railway companies as to life, cost of repairs and maintenance of rolling stock, and if these figures were from time to time published under some such system as that proposed recently by Mr. Crompton, it would materially conduce to the rapid advance of the electric lighting industry. A table was also given of the cost per annum of eight candle power lamps at 8d, per unit, burniug for a given average of hours at a stated efficiency; and a table of the insulation tests of internal wiring taken with too volts, and using an Evershcd ohm meter, which showed very clearly how the resistance varies in an inverse ratio to the number of points at which lights are taken off the house circuit.
It amiears that within the last eighteen months no miles of cable nave been laid or drawn in to conduits; and although the public have doubtless been much inconvenienced by the general upheaval of the street surfaces, yet, allowing for the immense amount of work that has been done, we think that it has lieen carried out with great celerity. The chairman. Sir Frederick Bramwell, referred to his own personal experience of the use of the electric light, and raised a point which is worthy of attention, namely, that the ease of switching the electric light on and off led to much less waste than with gas. He stated that in his own house he has an equivalent of 114 lamps of 8-candle power, and that he finds his light account from £20 to £25 more per annum than before; but that in the summer quarter the account was only about seven or eight shillings in excess of that for the previous year, when the electric light was not used. He left altogether out of consideration any allowance for diminished expenditure on redecorating the interior. Only 1000 arc lights are said to be used in the metropolis; and as was remarked by Mr. Mordey. it appears somewhat strange that street lighting is making such slow advances. For although streets like the Strand are not so favorably situated as some of the continental boulevards, yet arc lighting would vastly improve the metropolis. The existing prejudice against the use of overhead wires for electric lighting seems to be due to the exceedingly bad work done in the States, and notably in New York. The Metropolitan Electric Supply Company here has had twenty-five miles of overhead wires working fora considerable time without a single hitch or accident.
The vast increase of work in electric lighting can be judged by the statement that an addition of about 4000 lamps of 8-candle power is being made per week in London alone, and that there are now about 179 000 lamps of thirty-two watts each supplied from the mains of public supply companies, and about 85,000 by private plants—the large proportion of the latter being doubtless due to the repressive influence of the act of 1882.— J’he Engineer, London.
SAND FLOATING ON Water.—It is well known that a needle can be placed gently upon the water so as to float, the force of capillary attraction producing a surface tension so as to prevent its sinking. i‘he principle apparently accounts for the following phenomenon described by J. C. Graham in The American Journal of Science for December. He saw sand being removed from a bar jutting out from an island in the Connecticut river. The erosion, carried on from the side of the bar against which the current did not strike, took place by gentle ripple waves splashing up against the sand bar (which was at an angle of about 150 degrees to the surface of the water), and upon the retiring of each wave a little float of sand would be on the water. At first these were about the size of a silver quarter of a dollar, but by the union of a number, some floats would be formed of about six inches square. These blotches were so numerous as to be very noticeable in rowing up the river, and could be traced for half a mile or more below the bank, from which the sand came, although this was but a few yards long. If one of the blotches were disturbed by touching, or too violent action of the waves, it would immediately separate, the particles at once falling to the river bottom.
The above facts seem to show that coarse sand can be floated away by a current of far less velocity than 0.4545 miles per hour. They indicate a possible explanation of the coarser particles of sand occasionally found in otherwise very fine deposits.
A NKW I ROCF.SS OK RAISING Sand.—An improved process of raising sand has lieen patented in Great Britain by I*, lfampson of Belfast, Ireland, The inventor employs a barge having a tank to receive the sand or gravel to l>e raised, and a cistern ami waterhole to receive drainage or overflow of water therefrom. A pulsometer, or other pump, is provider! and furnished with a suction pipe—part rigid and part flexible—to reach to the l>ed or bank of sand, which is drawn through it and deposited in the tank. Around the mouth of the suction pipe arc placed a number of hollow prongs, suitably connected with another pulsometer or pump. Through these prongs jets of water, from the waterhole of the barge, are forcer!, so loosening the sand to allow it to be more readily taken up by the suction pipe.