Then scratch with a bit of flint, or with a writing-diamond, if you have one, a number on the end of the slide, and have a note-book with a corresponding number opposite to which you enter the description at a fuller length, thus:—
18—Scales of Death’s Head Moth (Acherontia Atropos), from centre of
under-surface of right fore wing. Dry. June 4, 1864. +
The cross signifies that you prepared the object yourself, and the reason for adding the date is, that in after years you will have a valuable guide as to the durability of your preparations. If the specimen has been purchased or presented, always add the name of the seller or donor, as well as the date. These precautions may seem to be needlessly minute, but we have so often seen whole sets of valuable preparations rendered useless for want of ticketing, that we cannot too strongly impress on our readers the necessity for the note-book as well as the label, the one acting as a check upon the other. When the label has been affixed, and the details transferred to the note-book, the ink may be washed off the end of the slide.
There is another convenient method of putting up the elytra of beetles, parts of various insects, mosses, minute shells, and similar objects. Take a common pill-box of the smallest size, and cut a little cylinder of cork, that will nearly, but not quite, equal the height of the box, and fasten one end to the bottom of the box with glue. Now blacken the interior of the box and the cork cylinder. Put a little drop of Canada balsam, Arabian cement, or gum Arabic on the top of the cylinder; put the object on it, press it into its place, and, when the cement is hard, the preparation is complete. The cover of the box serves to keep the object from dust.
Now we come to the Canada balsam, a substance which produces beautiful effects when rightly handled, but is most aggravating to the learner, causing alternate irascibility and depression of spirits. Many objects, such as the antennæ and feet of insects, will not show their full beauty unless they are mounted in Canada balsam. The method of doing so is as follows:—A week or two beforehand put the objects into ether or spirits of turpentine, and allow them to remain there until wanted. Pile up some old books, or take a couple of convenient wooden blocks; lay your brass plate upon them; light the spirit-lamp, and put it under the plate so as to heat it. Lay two or three slides on the plate, and all then can be heated at the same time.
Warm the bottle of Canada balsam, and with a glass rod take out a very little drop, and put it exactly in the middle of the slide. In order to insure this point, I always put a dot of ink on the wrong side of the slide. Stir it about with one of the needles mentioned on [page 428], and if any bubbles rise, break them. When the balsam is quite soft and liquid, take one of the objects out of the bottle and put it into the balsam, exactly over the black dot. Now add a little more balsam, so as to cover it, and let it lie for a few moments. Take one of the glass covers, put a very little balsam on its centre, and lay it neatly over the object, pressing it down gradually and equally. Unless this be done, the object will not remain in the centre, but will shoot out on one side, and the whole operation must be begun de novo. Remove it from the hot plate and lay it on a cool surface, still continuing the pressure until the balsam has begun to harden. Lay a little leaden weight—a pistol-bullet partly flattened is excellent for the purpose—and on the cover write the name of the object, as already mentioned, and then proceed to prepare another slide.
Twenty such slides may be prepared in the course of a morning, and when they are finished they should be laid carefully in a cold place, where they will be free from dust. In a week or so the balsam will be quite hard, and then the slide may be completed. Take an old knife, which should be kept for this special purpose; heat the blade in the spirit-lamp, and then run it along the edges of the slide, so as to take off the superfluous balsam which has escaped from beneath the cover. This must be done very quickly, or the balsam inside the cover will be heated by the knife, and the preparation spoiled. When this is done, cut the ornamental paper, as already described, number and label the slide, wash off the ink, and then the preparation is complete. Some objects are very troublesome to prepare, and require to be soaked in turpentine and boiled repeatedly in the balsam before they are completely penetrated with it.
Objects which are put up in Deane’s gelatine are managed after a similar fashion, save that the gelatine is to be heated by placing the bottle in hot water, and that the turpentine is not needed. Vegetable structures show beautifully when thus prepared. To remove the superfluous gelatine use a wet and not a hot knife.
Cells are very difficult to manage, and the novice had better not attempt to make them, but is hereby advised to purchase them ready made. Suppose that the young microscopist has dissected the digestive organs of a bee, and wishes to preserve it in spirit; his best plan will be to use a cell for the purpose. Let him buy a cell of sufficient depth, float the preparation into it, fill it up with spirit, put the cover loosely on, and leave it for a week, occasionally raising the cover and stirring the preparation with a needle, in order to get rid of any air-bubbles that may have been entangled in the tissues.