the ancients, has been long familiar to the artists of comparatively modern times,--so familiar, indeed, that it forms one of the first lessons of the drawing-master. The rule is a fixed one; but there is another rule equally important, not yet fixed,--that rule of proportion by which to determine the breadth which a certain extent of frontage between these converging lines should occupy. The principle on which the horizontal lines converge is already known, but the principle on which the vertical lines cut these at certain determinate distances is not yet known. It is easy taking the _latitudes_ of the art, if we may so speak, but its _longitudes_ are still to discover. At length, however, have we the lines of discovery indicated: in the architectural drawings of the calotype the perspective is that of nature itself; and to arrive at just conclusions, we have but to measure and compare, and ascertain proportions. One result of the discovery of the calotype will be, we doubt not, the production of completer treatises on perspective than have yet been given to the world. Another very curious result will be, in all probability, a new mode of design for the purposes of the engraver, especially for all the illustrations of books. For a large class of works the labours of the artist bid fair to be restricted to the composition of _tableaux vivants_, which it will be the part of the photographer to fix, and then transfer to the engraver. To persons of artistical skill at a distance, the suggestion may appear somewhat wild. Such of our readers, however, as have seen the joint productions of Mr. Hill and Mr. Adamson in this department, will, we are convinced, not deem it wild in the least. Compared with the mediocre prints of nine-tenths of the illustrated works now issuing from the press, these productions serve admirably to show how immense the distance between nature and her less skilful imitators. There is a truth, breadth, and power about them which we find in only the highest walks of art, and not often even in these. We have placed a head of Dr. Chalmers taken in this way beside one of the most powerful prints of him yet given to the public, and find from the contrast that the latter, with all its power, is but a mere approximation. There is a _skinniness_ about the lips which is not true to nature; the chin is not brought strongly enough out; the shade beneath the under lip is too broad and too flat; the nose droops, and lacks the firm-set appearance so characteristic of the original; and while the breadth of the forehead is exaggerated, there is scarce justice done to its height. We decide at once in favour of the calotype--it is truth itself; and yet, while the design of the print--a mere approximation as it is--must have cost a man of genius much pains and study, the drawing in brown beside it was but the work of a few seconds: the eye of an accomplished artist determined the attitude