3 i2 THE POPULAR SCIENCE MONTHLY. 



nected the study-rooms of two German scholars, has in fifty years 

 spread out into a network of wires that incloses the earth. The 

 length of the telegraph lines is estimated now at nearly a million 

 kilometres, and the length of the wires at more than double that 

 number. They stop for no obstacles, but find their way over mount- 

 ains covered with eternal snow, through deserts, and across rivers. 

 Even the sea does not stop them. More than seven hundred sub- 

 marine cables bear messages over the bottom of the ocean with a 

 speed outstripping that of the thought in which they originated. 

 Hard as it was fifty years ago even approximately to imagine the 

 impending development of the young discoveries and their influence, 

 it is just as hard now to comprehend them in their fullness. The 

 majority of living people take them for granted, and have no further 

 thought about them. Railroads and telegraphs have been so much a 

 matter of course to them from their childhood up that they can hardly 

 conceive that it was ever different. But he whose memory goes back 

 more than a generation, or whoever has traveled in countries where 

 mules or oxen are the only means of transportation, can realize the 

 difference and appreciate the importance of the progress, and the rela- 

 tions that exist between numerous phenomena of life and those con- 

 cerns. 



The most important and evident of these phenomena are the 

 changes which railroads and telegraphs as means of trade have 

 directly impressed on economical affairs ; their influences have also 

 made themselves felt, partly as consequences of those changes, in part 

 directly, in transformations of social conditions, and of manners and 

 customs. 



It is common to the means of transportation moved by steam and 

 to the telegraph that they effect changes of place, the former of 

 physical objects and men, and the latter of thoughts, with power, 

 speed, and security, immeasurably surpassing those of the formerly 

 known means. 



We will first consider the exchange of goods which composes 

 trade. In his latest "Review of the World's Economy," Dr. Van 

 Neumann-Spallart estimates the weight of the goods which the rail- 

 roads collectively carried in 1882 at about 1,200,000,000 tons ; the 

 freight of the steamers was calculated at about half that weight. By 

 far the greater part of these masses of goods have been set in motion 

 by trade in order to place them where they could be made of use. For 

 this reason, the figure of the weight, although the contemplation of it 

 overtaxes our limited powers of conception, gives quite as little idea 

 of the meaning of this enormous movement as does the knowledge of 

 the weight of the blood circulating in the body, with wdiich it is 

 customary to compare this trade, an explanation of the effect of 

 its flow. 



The extension of trade may be considered as to space and as to 



