Thus they can go at any rate of speed which they desire, instead of being limited in their movements by the powers of endurance of one set of animals, as they would be compelled to be if they were to travel with their own.

This plan has, for some reason, never been introduced into America, and it is now probable that it never will be, as the railway system will doubtless supersede it.
[Sidenote: Caesar's invasion of Britain.] [Sidenote: His pretext for it.] One of the most remarkable of the enterprises which Caesar undertook during the period of these campaigns was his excursion into Great Britain.

The real motive of this expedition was probably a love of romantic adventure, and a desire to secure for himself at Rome the glory of having penetrated into remote regions which Roman armies had never reached before.

The pretext, however, which he made to justify his invading the territories of the Britons was, that the people of the island were accustomed to come across the Channel and aid the Gauls in their wars.
[Sidenote: Caesar consults the merchants.] In forming his arrangements for going into England, the first thing was, to obtain all the information which was accessible in Gaul in respect to the country.

There were, in those days, great numbers of traveling merchants, who went from one nation to another to purchase and sell, taking with them such goods as were most easy of transportation.