and one of whose advisers is, or was, an individual whose business it was for the past two years to discredit the alternating system, for which service he was well paid. In no other city in the States or Canada is there such bad construction of overhead conductors as there was in New York. The under-ground construction there is nearly as dangerous on account of existing grounds on the wires and leakage of current and the consequent liability to cause explosions of gas in subways, as has already been repeatedly done, besides turning the paving stones into " a molten mass." Furthermore, the insulation of the overhead wires, which have been in use in some cases over eight years, had rotted off, being of the quality known as "Underwriters," or "Undertakers" if you will. Four deaths have occurred in the whole history of electric lighting in Canada from shocks of electricity, and two of these were the result of bad insulation of wires and faulty construction by a purchasing company doing its own work, without employing anybody having any knowledge of the business, in order to cheapen the first cost of the plant, and which purchased a job lot of poorly insulated wire, and ran two dynamos in series with 100 are lamps in circuit at a tension of nearly 5000 volts. The current used on that system was a continuous one, not a pulsating high tension current as stated in a circular which some of you may have received. Reverting to the main subject: Thirty wires radiate from the Valleyfield station; one pair carry the current from the Barrie station. In the Barrie station the pressure of primary current is the highest which has yet been used in this country, being about 2100 volts average on the feeder. This pressure is raised or lowered by increasing or decreasing the exciting current according to the load shown on the central station ammeter, which is graduated to single amperes, and is indicated by a Cardew voltmeter, which, as elsewhere mentioned, is attached through a converter to the armature. Instead of having a compensatoras is used in the Westinghouse system, a table of loads and the corresponding pressures to be carried at the station is used. This method, though of course not absolutely perfect, owing to the rise of current with increase of voltage and vice versa, answers very well. The Cardew voltmeter in the company's office in town, which is an excellent check upon the dynamo attendants' work, shows an average variation of two volts only in a night's run. The mains in town, which aggregate nearly 14 miles in length, are calculated for a loss of only 2 per cent. at full load, which gives a difference of of a volt per lamp up or down from the standard. The house wires, which are insulated with rubber and tape are calculated for one per cent. loss only at full load As most of the lights are taken in private residences, where the whole number are hardly if ever in use at one time, the loss of light through resistance of the house wiring is practically nil. MEASURING INSTRUMENTS. The Ayrton and Perry instruments have been used to a very considerable extent in this country, and until recently were the most accurate of all really portable electrical measuring instruments. There is a sample on the table before you. They are only suited for direct. currents, and are open to the objection that they have considerable friction and a high temperature error if kept in circuit, which they should never be except only for a few seconds when taking readings. The Weston voltmeter is shown in Figs. 25 and 26. These voltmeters have the great advantage of extreme accuracy and very high resistance, averaging about 20,000 ohms, so that the quantity of current pissing is extremely small. They may be kept continuously in circuit without any material variation in their readings. They require careful handling, of course, as do all electrical instruments, but they are the most accurate and reliable of all portable testing instruments for continuous currents. The voltmeters contain a calibrating coil by which their constancy can be at all times tested. The writer has used quite a number of these instruments which he has checked with cach other, and has sometimes compared the higher and lower scale by taking the P. D. difference between terminals of single cells of secondary batteries, and then, putting the whole of the cells in series, compared the reading of total E. M. F. of the battery. Several tests of this nature have come out within one quarter of a volt. The calibrations are in single volts on the higher scale, and thirtieths, twentieths or tenths of volts on the lower scale. The ammeters read to tenths of amperes in the small sizes. In both the divisions of the scale are so wide that one quarter of these values can be read with perfect case, For the most perfect readings by these instruments they should be set quite level, and five feet away from any other instrument, or from any mass of iron or steel, and so placed that the index will point due west when at the centre of the scale, but these precautions are not necessary for ordinary testing of pressure in build ings, as the error can seldom be more than volt, if otherwise placed. The Cardew volt meter (Fig. 27) is used for both direct and alternating currents, and is made to be used either vertically or horizontally. |