It might as well be remarked, in conclusion, that the size, and particularly the powers of the man-bats (for example, their ability to fly in so rare an atmosphere—if, indeed, the moon have any), with most of the other fancies in regard to animal and vegetable existence, are at variance, generally, with all analogical reasoning on these themes; and that analogy here will often amount to conclusive demonstration. It is, perhaps, scarcely necessary to add, that all the suggestions attributed to Brewster and Herschel, in the beginning of the article, about “a transfusion of artificial light through the focal object of vision,” etc., etc., belong to that species of figurative writing which comes, most properly, under the denomination of rigmarole. There is a real and very definite limit to optical discovery among the stars—a limit whose nature need only be stated to be understood. If, indeed, the casting of large lenses were all that is required, man’s ingenuity would ultimately prove equal to the task, and we might have them of any size demanded. But, unhappily, in proportion to the increase of size in the lens, and consequently of space-penetrating power, is the diminution of light from the object, by diffusion of its rays. And for this evil there is no remedy within human ability; for an object is seen by means of that light alone which proceeds from itself, whether direct or reflected. Thus the only “artificial” light which could avail Mr. Locke, would be some artificial light which he should be able to throw—not upon the “focal object of vision,” but upon the real object to be viewed—to wit: upon the moon. It has been easily calculated that, when the light proceeding from a star becomes so diffused as to be as weak as the natural light proceeding from the whole of the stars, in a clear and moonless night, then the star is no longer visible for any practical purpose. The Earl of Ross’s telescope, lately constructed in England, has a _speculum_ with a reflecting surface of 4,071 square inches; the Herschel telescope having one of only 1,811. The metal of the Earl of Ross’s is 6 feet diameter; it is 5 1/2 inches thick at the edges, and 5 at the centre. The weight is 3 tons. The focal length is 50 feet. I have lately read a singular and somewhat ingenious little book, whose title-page runs thus: “L’Homme dans la lvne ou le Voyage Chimerique fait au Monde de la Lvne, nouellement decouvert par Dominique Gonzales, Aduanturier Espagnol, autrem?t dit le Courier volant. Mis en notre langve par J. B. D. A. Paris, chez Francois Piot, pres la Fontaine de Saint Benoist. Et chez J. Goignard, au premier pilier de la grand’salle du Palais, proche les Consultations, MDCXLVII.” Pp. 76.