In mechanics a wedge is an instrument which can be usefully employed only under favourable circumstances. It has many disadvantages. It is easily jammed. The driving power at the base must be considerable; much of the force is absorbed by the friction on the surfaces; the progress made is very slow; and if the surfaces encounter a more tenacious material they will be perforated. A wedge is intended chiefly for cleavage and disruption when less clumsy methods are not at hand. The defects of a wedge as a mechanical power at once became apparent to the British force which occupied Natal when war became inevitable. The cutting edge was inaccessible and liable to injury which could not be easily repaired; much trouble was anticipated from the presence of Boer commandos in contact with the surfaces; the base did not appear to be sufficiently well designed to receive the impact of the propelling force; and there were grave doubts as to the soundness of the material of which an important section of the wedge, namely Ladysmith, was constructed. It was therefore proposed by the military authorities that the Natal wedge should not be used as an instrument in the war. To this the civil government at Pietermaritzburg strongly objected on account of the evil moral effect which the abandonment of a considerable proportion of the Colony to the enemy would exercise upon the general situation in South Africa, and of the loss of prestige which the evacuation would entail in the minds of the natives, who numbered three-quarters of a million. Under pressure from the Colonial Office, and against its own judgment, the Army of Natal set itself to work upon the Wedge. The mistake soon became manifest, although the artisans did their best. The Wedge was not an effective instrument; its cutting edge was never in operation; and in a very few weeks it was hewn into a mangled, cumbrous and irregular mass, which could neither be advanced nor withdrawn and which for nearly five months led a precarious and unhappy existence. Its distress necessitated the recasting of the plan of the South African campaign and a pernicious "moral effect" was not avoided. One British Army besieged in an open town surrounded by heights, while another was lying impotent upon the banks of the Tugela, eighteen miles distant, was the result of a few weeks' work with the Natal Wedge, which had been forced by the civilian strategists into the reluctant hands of the troops.[17]