Page:Hardwicke's Science-Gossip - Volume 1.pdf/228

Fresh-water Aquaria.—In reply to F. C. the bottom of the aquarium should have first from twenty to fifty small pieces of charcoal strewed over it; upon that about an inch in depth of well-washed sand, in which the plants should be planted,—over the sand near an inch of the smallest stones or pebbles; minnows and sticklebacks are the best fish to stock with, being the hardiest, living the longest in confinement, and they agree well together. I have minnows now that I have had at least two years. They should be fed with animal food; any kind of cooked meat not fat; two or three pieces to each fish (about double the size of a pin's head) each time of feeding. I feed mine about every five or six days. Some minnows I have are so tame they will take food from the fingers. I have kept stickle-backs more than twelve months; the very small ones do better and live longer than the large ones; sonic I have caught about half an inch long, have lived until quite an inch and a half. A few snails should be kept in the aquarium with the fish; they assist to keep the water clear and cat the decayed plants. They breed, and the young ones, and also their spawn, er eggs, find food for the fish. When they die they are eat by the fish; there is no fear of their contaminating the water. No doubt fish will live a long time without any food but what they find in the water, but they thrive much better with occasional feeding. In my aquarium the water has not been changed since May, 1863; every month or two I put in about a pint to replenish what it has lost from evaporation; and it is now beautifully clear.—Thomas Armstrong, Manchester.

Bull's-eye Condencser.—Will you allow me to suggest a cheap and very effective condenser for the microscope for viewing opaque objects. I have tried, I think, every kind made, and find this better than most, and I think as good as some very expensive cues. I use a glass globe about three and a half or four inches in diameter, filled with clear spring water, inverted upon an ordinary wine-glass. With a series of them filled with various coloured waters, I have had some very beautiful effects. Mine cost me 1s.—Thomas Armstrong, Manchester.

Pollen of Evening Primrose.—I do not recollect seeing the Evening Primrose named among the flowers whose pollen grains form beautiful microscopic objects, and would advise those of your readers who take an interest in these matters, and have not already a slide of it in their cabinets, to mount one in balsam, and another as an opaque object. The flower being so common there is no difficulty in procuring it in most places.—E. G., Matlock.

On Stage Forceps.—Having been much inconvenienced by the unsteadiness of the stage forceps of the usual construction, I set my wits to work to make a better; and after some trials bit upon the following, which appears to me so simple that any one may make it for himself. The annexed diagram scarcely needs explanation: A represents a piece of wood B, a hole for the reception of C, the forceps-holder, fastened by its screw; D, the forceps, passing through a hole in the piece of wood and the spring tube of the holder; thus the forceps have a smooth rotatory motion on their own axis, by which

any small object held therein can be viewed on almost all sides. To fasten the forceps to the stage I make a slit, E, near the bottom of the wood, which slips over the sliding-bar of the stage; by replacing the wood by a metal plate, the forceps could then he laid on the stage like a slide and the object rotated, without going out of sight, as was often the case with the old-fashioned forceps. I have found the above to answer admirably. For examining such things as flies' legs, heads, and probosces, with the binocular instrument, as opaque objects, the effect is very good, and the investigation can be made with much greater comfort and precision than with the old stage forceps.—A. J. Roberts.