Page:Popular Science Monthly Volume 5.djvu/327

Rh of each other to "solidify," reject the instrument; but, if they meet well when farther apart, the fault was in the pictures.

A friend complained to me that the stereoscope she had bought, on my recommendation, was worthless. I had taken it on faith, supposing that all "Holmes" instruments must be good; but a short examination showed that the glasses were rather flat, and were placed so near together that the rays came to the eyes through the central part of the lens, and of course without refraction, and hence the eyes were not deceived. By whittling out the frame, and moving each glass outward about three-eighths of an inch, a good instrument was made.

If a view does not "stand out well" when seen in a good instrument, examine each picture by itself, and try to find a well-defined object, as a post or tree, in the foreground, and note its relations to some other object in the distance. If the two objects have the same relative position in both, the pictures are duplicates, and worthless.

If the distant object is to the right of the near one, they should appear farther apart in the right-hand picture, and vice versa; if not so, the pictures are mounted on the wrong ends of the card, and are worthless, or worse.



HE subject selected for this evening's entertainment—the evolution and metamorphoses of organic forms, from the genesis of life up to man—with all its difficulties, might, in skillful hands, be made amusing; but, let us rather hope for the earnestness, however dull, which will instruct, instead of the light talent which can while away an idle hour. It is a subject which has escaped from the pin-fold of the learned, and become public property, at least in part; and we see it engaging the attention of news-mongers, writers of squibs, and makers of woodcuts, as well as the graver interests of literary circles, and the thunders of the pulpit.

And here let us pause a little to place ourselves right with ourselves, and right with the rest of the world.

As it is proposed to view this matter, there is not one particle of religious interest in it, any more than there would be in a lecture on geology, chemistry, or any other pure science; and, in the name of truth, system, and logic, I must protest against the unscientific, 