the assimilation of carbon and the evolution of oxygen result. . . . .
"He had satisfied himself that in fine weather a plant consisting chiefly of leaves and stem will, if confined in the same portion of air night and day, and duly supplied with carbonic acid during the sunshine, go on adding to the proportion of oxygen present, so long as it continues healthy, at least up to a certain point. . . . .
"Considering the quantity of oxygen generated by a very small portion of a tree or shrub introduced, he saw no reasons to doubt that the influence of the vegetable might serve as a complete compensation for that of the animal kingdom."
In 1837, Mr. Ward made a Report to the British Association, "On the growth of Plants in closed Cases," at the end of which he "directed the attention of the members to the development of animal life upon the same principles." He was "quite certain that a great number of animals would live and thrive under this treatment."
In his treatise on the same subject, published in 1842, he dilates a little on this matter, chiefly with regard to increasing the purity of air for breathing in large towns, as a remedy for disease. "The difficulty to be overcome," he observes, "would be the removal or neutralization of the carbonic acid given out by animals; but this in the present state of science could easily be effected, either by ventilators or by the growth of plants in connexion with the air of the room, so that the animal and vegetable respirations might counterbalance each other. The volume of the
