_Eub_.--I doubt much whether it is for the interests of a people that its public works should be of a durable kind. One of the great causes of the decline of the Roman Empire was that the people of the Republic and of the first empire left nothing for their posterity to do; aqueducts, temples, forums, everything was supplied, and there were no objects to awaken activity, no necessity to stimulate their inventive faculties, and hardly any wants to call forth their industry. _The Unknown_.--At least, you must allow the importance of preserving objects of the fine arts. Almost everything we have worthy of admiration is owing to what has been preserved from the Greek school, and the nations who have not possessed these works or models have made little or no progress towards perfection. Nor does it seem that a mere imitation of Nature is sufficient to produce the beautiful or perfect; but the climate, the manners, customs, and dress of the people, its genius and taste, all co-operate. Such principles of conservation as Philalethes has referred to are obvious. No works of excellence ought to be exposed to the atmosphere, and it is a great object to preserve them in apartments of equable temperature and extremely dry. The roofs of magnificent buildings should be of materials not likely to be dissolved by water or changed by air. Many electrical conductors should be placed so as to prevent the slow or the rapid effects of atmospheric electricity. In painting, lapis lazuli or coloured hard glasses, in which the oxides are not liable to change, should be used, and should be laid on marble or stucco encased in stone, and no animal or vegetable substances, except pure carbonaceous matter, should be used in the pigments, and none should be mixed with the varnishes.