That such information would be desirable, we were led to believe from the surprise expressed by an intelligent friend at the definition given him of the phrase 'line of battle.' He was greatly astonished on learning that battles are fought, mostly, by lines of only two ranks in depth. The history of the 'line of battle' is of great interest, and indeed contains an exposition of the principles on which a great portion of modern warfare is founded. While the chief principles of strategy, of the movement of armies, of attack and defence, and to some extent of tactics, are the same now as in the earliest ages, the mode of arraying men for battle has undergone an entire change, attributable to the improvement in the weapons of warfare. We are not superior to the ancients so much in the science of war, as in the character of our arms. They undoubtedly fought in the manner most appropriate to the means which they possessed. The great change which has taken place in the method of battle, consists chiefly in this--that formerly men were arrayed in masses, now in lines. The Grecian phalanx was composed of 32,000 men arranged as follows: 16,000 spearmen placed in sixteen ranks of a thousand men each, forming the centre; on each wing, 4,000 light spearmen in eight ranks; 4,000 men armed with bows and slings, who performed the part of skirmishers; 4,000 cavalry. The Roman legion contained 4,500 men, of which 1,200 were light infantry or skirmishers armed with bows and slings. The main body consisted of 1,200 spearmen, who were formed into ten rectangular bodies of twelve men front by ten deep; behind them were ten other rectangles of the second line; and behind these a third line of 600 in rectangles of six men front by ten deep. To the legion was attached 300 cavalry.