of practical invention - the business man to work them, and the 'labourer" to be wise enough to see that his work, being the least important, is paid for according to its worth. "No art or manufacture is so perfect as to be exempt from the influence of discovery and invention, and no man can produce so perfect an article, but that, by the aid of science, a better may be produced. Science and trade are mutually dependent : without the assistance of science, trade would be unable to supply our daily increasing wants; and without the pecuniary support of trade, science would languish and decay. As long as arts and manufactures are left to be directed and improved by simple experience, their progress is extremely slow; but directly scientific knowledge is successfully applied to them, they bound forward with astonishing speed. Look at the art of taking portraits: for hundreds of years it remained entirely in the hands of oil and water colour painters, with but little progress in rapidity of production; but directly science was applied to it in the form of photography, its advance in this respect became amazing. Fifty years ago, photography was almost unknown; but immediately Messrs. Daguerre and Talbot, in 1844, made known their processes, the new art began to advance, and so rapid has been its progress, that at the present time many thousand persons are employed in its exercise, and millions of portraits have been taken with an accuracy and at a cost quite beyond the reach of the old method. By investigating the chemical action of electricity upon saline bodies, Sir Humphrey Davy isolated sodium and magnesium, which has led to the establishment at Patricroft, near Manchester,