58 



SCIENCE. 



[N. S. Vol. XVIt. No. 419. 



especially is this the case if the exhaust 

 steam be used for heating purposes. In 

 isolated plants the cost of transmission is 

 very small as compared with the total cost 

 of generation; whereas in the average cen- 

 tral station the cost of transmission, which 

 includes interest and depreciation on pole 

 line, usually constitutes a large percentage 

 of the operating cost. 



In those localities where the cost of fuel 

 is high, electric power can often be pur- 

 chased more cheaply from a central sta- 

 tion which obtains its power nvmy miles 

 distant and transiuits it elect. lUy to a 

 convenient distributing center, .vuere it is 

 used for power and light. 



The recent development in electrical 

 transmission is very marked, and one 

 constantly hears of some new achievement 

 more wonderful than anything previously 

 accomplished. Distances have been gradu- 

 ally increased until it is now possible to 

 transmit electrical energy economically and 

 in commercial quantities up to 150 and 

 even 200 miles. 



There has been a steadily increasing 

 tendency to raise the line voltage in such 

 transmissions, and to-day we find in suc- 

 cessful operation voltages as high as 40,000 

 and even 60,000 as compared with the 

 4,000 and 6,000 volts of a few years ago. 



As pointed out by Mr. A. D. Adams,* 

 so far as present practice is concerned the 

 limit of use of high voltages must be 

 Sought beyond the transformers and out- 

 side of generating and receiving stations. 

 As now constructed, the line is that part 

 of the system where a final limit to the 

 use of higher voltages will first be reached. 



In order to avoid the temporary arcing 

 and leakage between the several wires it 

 is necessary to place the wires a consid- 

 erable distance apart, which, with higher 

 voltages, may lead to a modification in 

 construction of pole line. The plan of 



* Eiiri. Mag., October, 1902. 



substituting a series of steel towers about 

 90 feet in height and 1,000 feet apart is 

 being seriously contemplated.* 



In this ease it is proposed to suspend 

 the wires from tower to tower and separate 

 them about nine feet apart. While ex- 

 pensive in first cost, it is thought that the 

 satisfactory working of the system and 

 freedom from breakdown, with the low 

 maintenance and depreciation charges in- 

 volved, would warrant the investment. 



A more serious difficulty is found in 

 the insulator, which is generally looked 

 upon with distrust for the higher voltages 

 in use to-day. With a more perfect in- 

 sulator there would appear to be no good 

 reason why the present maximum voltages 

 should not be exceeded. 



The possibility of electrical transmission 

 thus permits of the utilization of available 

 sources of power at great distances from 

 the center of distribution; but while it is 

 interesting to know that a certain amount 

 of power may be transmitted a given dis- 

 tance with a high degree of efficiency, it 

 is more important to know whether the 

 same amount of power could be obtained 

 at the objective point more economically 

 by other means. 



It has been suggested that the future of 

 long-distance transmission depends largely 

 upon the development of oil as a fuel; but 

 at the present time the outlook for oil fuel 

 in general competition with coal or long- 

 distance transmission is not encouraging; 

 while the development of the Texas and 

 southern Califoimia oil fields has increased 

 the visible supply and brought about in- 

 creased activity in the use of liquid fuel, 

 yet it is doubtful whether the advantages 

 would be sufficient to cause it to come into 

 general use as a fuel, since with a limited 

 production and an increased demand for 



* Geo. H. Lukes in Tran^. Assn. Edison Illu- 

 minating Companies, July, 1902. 



