up the soliciting department into distinct branches. The popular method of keeping track of the solicitors' work is through the medium of reports which are forwarded daily to a record clerk at the main office for file and follow up. Advertising costs of the member companies varied from 0.25 per cent to 2.50 per cent of the gross revenue, the average figure being 1.25 per cent. An analysis of the answers received shows a considerable unanimity in thought regarding the most efficient method of expenditure, and a composite opinion upon the handling of a given appropriation would be approximately as follows: Spend three-fifths upon a follow-up campaign of direct-mail advertising; spend one-fifth upon newspaper and street-car advertising; spend one-fifth upon miscellaneous advertising, including bulletins, stuffers for bills, and so forth. As bearing upon the new-business staff and expenses that a company can and ought to carry, it may be noted that in Denver every $1.00 spent on the new-business department brought in $3.00 increase in gross income. This applied to the electrical earnings only. The increase in peak load of December, 1905, as compared to December, 1904, was 35 per cent. The load-factor remained about the same, being 40 per cent in one case and 42 per cent in the other.

OLD AND NEW LAMPS

The tendency toward heterogeneity in electric lamps, noted in the reports of 1905 and 1906, has been very marked during the past year, and one must go back nearly four decades to find conditions of uncertainty and experiment corresponding to those that now prevail in the field of illumination. The range of possible lamps in both the arc and the incandescent departments has been marvellously enlarged, and to these peculiar forms others of a new character have been superadded. For many of the newcomers claims of superiority are put forward of a striking nature, and if all these claims were well founded the older lamps might soon pass out of service. "When the gods arrive the halfgods go"-but it has still to be proven that the essence of immortality dwells exclusively in the novelties of which just now so much is heard. The trying-out process must soon begin, equal to that which has tested present lamps since 1880 and brought them to their high efficiency. Probably a place will exist for all. The human

race has never yet discarded an illuminant once found, and it is extremely difficult to believe that the old arc lamp and the old carbon-filament lamp are to be relegated to the obscurity they have destroyed.

So many conditions are involved in a change from one set of fundamental apparatus to another, the period of transition. must necessarily be long even if the expected improvements make good. The era of electric traction is well begun, but the steam locomotive, and even the horse-car, still prevail. As a matter of fact, it is more interesting and practical to watch the actual incipient changes than to speculate on the possible scope of a whole revolution. For instance, there is an indication that a change in the art is upon us in the scarcity of old-style standard 32 and 50-cp lamps, due to the fact that makers are getting ready to discontinue their manufacture. The lamp manufacturers announced their intention some time ago of discontinuing the manufacture of the old common carbon-filament lamp in sizes of over 100 watts because of the advent of the new graphitizedfilament lamp now commonly known as the "Gem," which latter, because of its higher efficiency, would be certain to supplant the old standard lamps even if the manufacture of the old lamps was not discontinued. But here comes in one of the prosaic points of detail. The position of the man who has an installation of standard 32-cp lamps with standard shade holders and who must. substitute the new lamp, which is considerably larger in bulb. and longer in neck than the old standard 32-cp lamp, is not a profitable one. The new lamp, as made, requires special shade holders when fitted with reflectors. The old standard shade holders leave the shade "high and dry" above the lamp bulb, defeating most of the purposes for which the shade may be intended. If the change to larger bulb lamps requiring different shade holders causes the owner at the same time to change to glassware that is suited to the purpose of most efficient illumination, the change in lamp sizes will have been a good thing aside from all questions of lamp efficiency.

Reference has just been made to the graphitized-filament lamp, which may be regarded as an example of the ability of the carbon filament to adapt itself to more modern conditions of environment and competition. Another newer lamp of the same

generic high-efficiency character is the "Helion," the result of several years of research work by Messrs. Parker and Clark in the Phoenix Physical Laboratories of Columbia University, New York city. The name was adopted on account of the resemblance of the spectrum from this filament to the solar spectrum. In some respects the filaments are quite remarkable, as they are not metallic, yet they can be operated at a specific consumption of one watt per candle at a temperature which readings on the absorption pyrometer indicate is very much below the temperature of metallic filaments when operated at this consumption. The Helion filament is composed largely of silicon reduced and deposited, together with the other materials, under very exact conditions. The base that is being used at present is a special carbon filament, on which the necessary deposit is made. The filament is mounted within a globe which is then pumped out, in much the same manner as with the ordinary carbon lamp. When current is applied, the first noticeable characteristic is the white light radiated from the filament at a current density at which the carbon filament would be radiating only red rays. The next characteristic is the whiteness of the light, and the high luminous efficiency of the filament at its normal current density, and next the overload or extra current that it will carry without breaking down. The filament, while not metallic in the proper sense, shows a metallic characteristic in that it is possible to fuse parts of it together very much the same as is done with a metallic filament. Lamps of this style have shown under test lives of from 485 to 1270 hours of actual burning. It has been found possible to make Helion filaments as low as 30 candle-power for present commercial e.m.f., of from 100 to 115 volts, of approximately the same length as ordinary carbon filaments.

It is also worthy of note that these two experimenters have also in process of active development an interesting form of lamp for constant-potential circuits the light of which is developed in a conducting film lining the bore of a small quartz tube. In regard to this lamp, one of the points that has attracted the notice of the United States Government experts is its adaptability for use where there is violent concussion from the firing of ordnance, which is destructive of the ordinary incandescent lamp. The

heavy quartz tube will withstand such shocks, and a vacuum is not necessary. An interesting feature of the lamp is that the quartz permits the passage of the short wave-lengths of ultraviolet light. The conducting film gives off a quantity of such rays, and it is found that the efficiency of the lamp can be increased by coating the surface of the tube with thorium oxide. Under the combined effect of the heat and the ultra-violet rays it then glows with the characteristic light of the Welsbach mantle. The specific consumption with the plain tube is placed at about 2.5 watts per candle.

As to actual carbon-filament lamps on the market, and the drift away from 16-cp units as too low, Mr. F. W. Willcox, in a recent paper before the Vermont Electrical Association, stated that a new standard 50-watt lamp giving 20 candle-power mean horizontal has been made to comply with the wishes of the leading central-station companies, who asked the improvement in efficiency given in the form of 25 per cent increased candlepower, with the total watts per lamp unchanged. This is perhaps a more apparent improvement than a 20 per cent reduction in watts per lamp would be. The movement appears to be away from a 16-cp standard. It is not enough in many cases, and in other cases it is too much. Mr. Willcox described also the commercial tantalum lamp at some length and presented a table comparing its qualities with the new high-efficiency graphitizedfilament units. Thus far the only available tantalum lamp in this country is the 22-cp, 44-watt size. The useful life on direct current is about 700 hours, and only about 200 hours on alternating circuits. The lamp burns to best advantage in a pendent position. It is not nearly as sensitive as the carbon-filament lamp to change of voltage. The tantalum lamp has a probable limit of 20 candle-power in very efficient sizes. It is somewhat more fragile than the carbon-filament lamp and suffers somewhat from vibration. Present prices of tantalum lamps hardly permit free renewals.

As to the price of the tantalum lamp, the practice of the New York Edison Company may be cited. It has notified its customers that the 44-watt, 22-cp lamp is available, giving 37.5 per cent more light while consuming 12 per cent less energy. Retail customers of the company enjoy free lamp renewals, but

of course that rule does not apply to the metallic-filament lamp. While the tantalum costs at retail 60 cents, the company is furnishing its retail customers with the lamp at the net price of 35 cents. Edison customers purchasing electricity under any of its wholesale forms of contract may purchase their own incandescent lamps independent of the purchase of electrical energy. The difference is allowed for in the wholesale as compared with the retail price schedules; and such customers may purchase the tantalum lamps from the company at the net price of 48 cents each.

Meantime, the tantalum lamp is ceasing to be a novelty, being seen on so many circuits, and tungsten lamps are looming up, with yet others in an advancing host. An excellent summary of the situation was presented in November before the American Institute of Electrical Engineers by Dr. Clayton H. Sharp, who held that the standard of incandescent lighting efficiency would be brought by the tungsten lamp to a point three times as high as at present, although it might be found less adapted to use on 25-cycle alternating circuits than the standard lamp of to-day. The tantalum lamp at present is essentially a direct-current lamp. Dr. Sharp quoted a foreign test on tungsten lamps, one of which reached the extraordinary life of 3537 hours, with a decrease in candle-power of about 10 per cent.

With reference to the physical characteristics, tungsten lamp filaments, he said, manifest all the ordinary properties of wires of pure metals. They have a high conductivity and a large positive temperature coefficient. The former characteristic requires that the filaments be very fine and quite long if they are to be used in producing lamps giving a reasonably low candle-power on 110-volt circuits. The filaments are, moreover, quite soft at the temperature of full incandescence, so that it is not feasible to mount them in lamps in any other form than in loops. The first tungsten lamps produced were designed for low voltages, and in consideration of the high conductivity of the material this is a simpler problem than the production of lamps for higher voltages, since in the former case a shorter length of the filament may be employed. It is also easier to produce a lamp of high candle-power than of low candle-power, since a stouter filament may be employed in the high-candle-power lamp.