Page:Popular Science Monthly Volume 44.djvu/58

50 Gas may be counted upon for a duty of seventy-five per cent; so that the amount necessary to do the heating work of the electrical horse power will be five and a third feet. This, with gas at a dollar and a half per thousand will cost ·078 of a cent, and with gas at a dollar a thousand—a not uncommon price at present in the United States—will cost but little more than half a cent. For cooking purposes the two methods of heating are on an equality in the matter of ease of manipulation, absence of collateral expenses, and limitation of the use of the fuel to the exact time required to perform the operation in hand. Their value to the householder is, therefore, in direct ratio to their cost. Gas clearly has the advantage of being from five to ten times the cheaper source of heat, an advantage so great as to make its supremacy secure. With the cheaper forms of fuel gas which have grown up, and will doubtless come into larger and larger use as the lighting field of gas dwindles, electricity can have even less chance of competing. This method of heating will doubtless find a field of its own, in which its use will be determined by other conditions than those of economy, but it can never hope to take over to itself any considerable part of the heating domain, so long as fuel remains at anything like the present prices.

The Centennial left us in the telephone a new method of communication, which in the time since then has grown into one of the necessities of business life. The Columbian will leave us, in the telautograph of Prof. Elisha Gray, another method of communication which promises to rival the telephone in utility. This new method is not exclusive of the earlier one, but rather supplementary to it. The telephone has endowed us with the power of talking at a distance; the telautograph will confer upon us the ability to write in the same way. It supplies an essential feature lacking in the telephone—a record—and hence becomes available for many uses for which the telephone is unfitted. Mistakes so liable with speech transmission are here impossible, as the receiving instrument reproduces faithfully all the movements of the transmitting pencil, and only a blunder upon the part of the sending operator can cause misunderstanding or confusion. With telautograph exchanges established in cities after the manner of those of the telephone, it will be possible for subscribers to do by means of it much of the correspondence now carried on by mail; and when the system is extended to provide communication between cities, the business man will have at his disposal a method of letter transmission incomparably more swift than the most rapid of fast mails. The extent to which such a system may be used in substitution of mail service will, of course, depend upon the expense attending it, and as this must always be greatly in