Another instance of science applied to art--and not the least important--is the adaptation of glass to form the lens which enables the flame of a lamp to be seen from a great distance. What this has done for the mariner is shown in our lighthouses, which enable him to know where he is by night as well as by day, for the lights are made to revolve, to be stationary, or to show various colours or flashes, which reveal to him their respective positions. The compass also, though ancient, is still an application of applied science, and by it the mariner is enabled to guide his ship safely over the ocean. A very beautiful instance of applied science to art is electrometallurgy, in which metals are deposited by means of the galvanic battery in any required form or shape, and this process of gilding and plating is executed with marvellous rapidity. All these various instances show what the mind of man has done, and is doing; but the applications of science to art are so endless, that even their simple enumeration could not be included in the limits of an opening address, for there are few things to which science cannot be applied. One of the most recent and beautiful is the art of photography, where, by means of applied chemistry, aided by the rays of the sun, there can be produced the most pleasing and lifelike representations. This new application of chemistry is a most interesting one, which shows that we do not stand still, and as long as arts and science are permitted to be practised by us we are not intended to stand still, but to exercise our minds to the utmost to unravel those mysteries of nature that are yet to be developed. Chemistry, as a regular branch of natural science, is of comparatively recent origin, and can hardly be said to date earlier than the latter third of last century. The Greek philosophers had some vague yet profound ideas on this subject, but their acquaintance was limited to speculations _à priori_, founded on general and often inaccurate observations of natural occurrences. Yet their acuteness was such, that some of their speculations as to the constituent properties of matter coincide in a wonderful degree with those which now prevail among modern philosophers. It is not easy to define what chemistry is in a few words, but it may be described as the science which has for its object the investigation of all elementary bodies which exist in the universe, with the view of determining their composition and properties. It also seeks to detect the laws which regulate their mutual relations, and the proportions in which these elements will combine together to form the compounds which constitute the animal, vegetable, and mineral kingdoms, as well as the properties of these various compounds. The ancients admitted only four elements--earth, air, fire, and water. Chemists now far exceed this number, and seek to show what these elements are composed of by analysing them into the various gases, solids, and liquids.