In examining the question of economy in the use of steam-power instead of horses, we shall obtain valuable assistance from a paper addressed to Mr. J. T. Osborne, of Demerara, by the Council of the Highland Society. This paper sets the period of the productive labour of a horse against the unproductive period necessary for its rest, and exhibits results of a startling kind. Horses are fed and tended three hundred and sixty-five days of twenty-four hours, or eight thousand seven hundred and sixty hours in the year. But they work only three hundred days, of about eight hours, taking the average, or two thousand four hundred hours a year. Thus we have a clear loss of six thousand three hundred and sixty hours of unproductive feeding and tending. It may be argued, that they are not fed and tended throughout the night, and therefore there is no such loss as the figures displayed by the Highland Society; but they are fed and tended enough to suffice them during the night, for which no compensating work is performed, so that it comes, we think, to nearly the same thing. According to McCulloch, there are about one million two hundred thousand agricultural horses employed in Great Britain, which, at twenty-five pounds per head for maintenance, amounts to thirty millions sterling per annum for their keep. The unproductive portion, therefore, he finds amounting to the enormous sum of twenty-one millions seven hundred and eighty-five thousand three hundred and six pounds. It will be seen that this estimate is founded on the previous figures displaying the number of hours of feeding and tendence, compared with the number of hours’ work, and the consequent loss of six thousand three hundred and sixty hours. The only compensation for this loss of hours, represented by the above sum of upwards of twenty-one millions sterling, is in the value of the manure, which is thus produced at too great a cost. “There are insuperable difficulties,” writes the Council of the Highland Society, “attending the employment of vital power; but mechanical power puts forth its energy when called for--it can be regulated, and, at pleasure, stopped. If it is desired to occupy the entire hours of daylight--to extend the field of operations--to work up more raw material--the energy of the animal ceases after a time; but not so that of the machine. The longest hours of summer may be advantageously employed.” And why not in the shortest nights of winter also? Could not steam-ploughs be made to carry their own lights with Hale Thomson’s patent silvered-glass reflectors, like other locomotives?