ELECTRICITY AT THE WORLD'S FAIR. 733 



be grouped in various combinations. For the regular operation 

 of the boats the cells are grouped in three divisions containing 

 twenty-six cells each, arranged in series. 



The batteries are charged for a run of ten to twelve hours, and 

 are then recharged at the power station of the fleet in from five 

 to seven hours. The launches run over a course of about three 

 miles, at a speed of six miles an hour, and make landings at the 

 principal buildings, all of which front upon the waterways. 



To the engineer and to those who desire to know the trend of 

 electrical development, the most interesting exhibit at the Fair 

 will doubtless be the apparatus designed to show the long-dis- 

 tance transmission of power. Almost at the beginning of the 

 modern electrical era, dreams were indulged in of the command 

 which electricity was to give us of the natural sources of power. 

 Marcel Deprez, at the Paris Exposition of 1881, had in operation 

 a system of power transmission, and similar attempts have been 

 made at every important exposition since, the most elaborate hav- 

 ing been that at the Frankfort Exposition of two years ago. Of the 

 importance of the economic transmission of power over long dis- 

 tances there can not be two opinions. The modern world has 

 come to rest down upon an abundant and cheap supply of power 

 in such a measure that without it civilization itself would go by 

 the board. Statisticians have frequently shown that the coal sup- 

 ply, while large and ample for present needs, is not only exhaust- 

 ible, but is being encroached upon at such a rate as to make its 

 conservation a matter of grave concern. Electric transmission of 

 power, by opening up to civilization the enormous supply of 

 power of the waterfalls and running streams of the earth, will be 

 able to postpone indefinitely the evil day that would be ushered 

 in by the failure or material decrease of our fuel supply. To be 

 of avail, however, such transmission must be economical, not only 

 in the percentage of utilizable power sent through the line, but in 

 the investment which must be made to realize it. So long as we 

 were dependent upon the direct current, but little progress could 

 be expected in this important problem. It has only been, there- 

 fore, in the last few years that the art was ripe for the taking up 

 of this subject in a serious spirit, and with any hope of a real 

 solution. The direct-current dynamo, handicapped with the com- 

 mutator, is necessarily limited to supplying currents of relatively 

 low voltage; the economic transmission of power demands the 

 use of currents of small volume and very high pressure. This 

 means small line conductors, and hence a relatively small invest- 

 ment. It means also a small loss in heating the line, since the 

 heating power of the current varies as the square of the volume 

 transmitted. 



