50 THE POPULAR SCIENCE MONTHLY. 



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 electri- 

 cal 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 advan- 

 tage 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 con- 

 siderable 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 com- 

 munication, 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 commu- 

 nication which promises to rival the telephone in utility. This 

 new method is not exclusive of the earlier one, but rather supple- 

 mentary 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 receiv- 

 ing instrument reproduces faithfully all the movements of the 

 transmitting pencil, and only a blunder upon the part of the send- 

 ing 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 be- 

 tween 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 



