As the burghers retreated before the British advance they destroyed all the bridges on the lines of retreat in a most effectual manner by the use of high explosives, in many cases leaving hardly one stone above another. On the line from Cape Town to Pretoria the spans over the Orange, Riet, Modder, Vet, Vaal, and Zand rivers, besides many others, were destroyed, so that it took weeks to repair them; and in all cases the British were compelled to build deviations of the line going around the banks of the rivers, and by gradual descent into the bed of the river and then up the opposite bank. Nearly all the river beds of the Orange Free State and the Transvaal are very deep, with perpendicular sides. Their depth is so great that it is quite impossible to cross at any point except by the railway bridges and the regular fords and drifts. One may ride almost to the edge of the river before realizing that there is a stream in the vicinity. The laborious difficulty of spanning these deep gorge-like river cuts makes it necessary that a large body of troops be detailed to guard each bridge or line deviation. The railways must be maintained or the advance must withdraw. [Illustration: Defense of a line of communication in the Transvaal.] There is a striking contrast between the methods of our government and that of the various European powers in the treatment of practical problems regarding the mobilization of troops in time of peace. There is not a state of the Old World so small as to be without its manœuvres, and as the great agency the railroad facilities are carefully studied. It has been a huge military oversight on the part of our government to fail to provide for an occasional mobilization of troops, and for their operation in the field as one body. We have never had an army of sufficient size to warrant any such manœuvres with the regular force alone, but the National Guard regiments should be included in this sort of work just as the militia regiments of England are every year made a part of the Aldershot manœuvres. It has been argued that our distances are too great to justify such an extensive plan of peaceful operations, but that very reason should be the incentive to our government to appropriate sufficient funds to carry on the work. It would be a simple matter indeed were the operations of our forces confined to as small a territory as those of England, France, or Germany; but when the sudden call of troops means a mobilization from many quarters and a journey of several days, to leave the problem to the last moment before solving it is indeed a perilous hazard and one that is incredibly irrational.