1598. Botanic gardens. The primary object of botanic gardens is to exhibit a collection of plants for the improvement of botanical science; a secondary object to exhibit living specimens of such plants as are useful in medicine, agriculture, and other arts; and a third is, or ought to be, the acclimatising of foreign plants, and their dissemination over the country. In choosing a situation for a botanic garden, the leading object must be proximity to the town, city, or university to which it is to belong; and the next, if attainable, a variety of surface and soil, to aid the necessary formation of composts and aspects for different plants. In general, however, there is little choice in these respects, it being sufficiently difficult to procure an adequate extent of surface of any kind near large towns. As the leading object or feature in the view of a botanic garden is the range of hothouses, and as these must always face the south, it is generally desirable that ground on the north side of the principal public street or road by which it is to be approached, should be preferred to ground on the south side. In the latter case, the hothouses must be approached from behind, and then the spectator must turn round to look at them, by which their grand effect is lost.