microscope. The common screw-moss may be found in great abundance, and shows this denudation of the spores very perfectly. Many of these may be easily dried without much injury, but they should also be examined in their natural state.

The student should not omit from his cabinet a leaf of the nettle and the allied foreign species, the mystery of which the microscope will make plain. The hairs or stings may also be removed, and viewed with a higher power than when on the leaf, being so transparent as to require no balsam or other preservative.

There are few more interesting objects than the raphides or plant-crystals. These are far from being rare, but in some plants they are very minute, and consequently require care in the mounting, as well as a high magnifying power to render them visible; in others they are so large that about twenty-five of them placed point to point would reach one inch. Some of these crystals are long and comparatively very thin, which suggested the name (raphis, a needle); others are star-like, with long and slender rays; while others again are of a somewhat similar form, each ray being solid and short. If the stem of rhubarb, or almost any of the hyacinth tribe, be bruised, so that the juice may flow upon the slide, in all probability some of these crystals will be found in the fluid. To obtain them clean, they must be freed from all vegetable matter by maceration. After this they must be thoroughly washed and mounted dry. They are also good polarizing objects, giving brilliant colours; but when used for this purpose they must be mounted as described in Chapter IV. A few plants which contain them may be mentioned here. The Cactaceæ are very prolific; the orchids, geraniums, tulips, and the outer coating of the onion, furnish the more unusual forms.

The Fungi are generally looked upon as a very difficult class of objects to deal with, but amongst them some of the most available may be found. The forms of many are

very beautiful, but are so minute as to require a high magnifying power to show them. The mould which forms on many substances is a fungus, and in some cases may be dried and preserved in its natural state. A friend of mine brought me a rose-bush completely covered with a white blight. This was found to be a fungus, which required a high magnifying power to show it. Being a very interesting object, it was desirable to preserve it, and this was perfectly effected without injury to the form by simply drying the leaf in a room usually occupied. Amongst the fungi are many objects well worth looking for, one of which is the Diachæa elegans. This, the only species, says the Micrographic Dictionary, is found in England upon the living leaves of the lily-of-the-valley, &c. These little plants grow in masses, reminding one of mould, to a height of a quarter of an inch, and each "stem" is covered with a sheath, in shape somewhat like an elongated thimble. When ripe the sheath falls off and reveals the same shaped column, made up of beautifully fine network, with the spores lying here and there. This dries well, and is a good object for the middle powers. Amongst the fungi the blights of wheat and of other articles of food may be included. Many of them may be mounted dry; others, however, cannot be well preserved except in liquids, and will be referred to in Chapter V. When rambling in a wood during the summer I sat down upon the fallen trunk of a tree, and here and there a few minute white spots caught my eye. I took my Coddington lens from my side-pocket and applied it to these. Judge of my surprise when I found each white speck a distinctly formed fungus resembling in size and form, to an amusing similarity, a disc of the arachnoidiscus. They were already dry, and I mounted them as ordinary dry objects; and hitherto no change has taken place which I can detect. Amongst the zoophytes and sea-mats, commonly called sea-weeds, may be found very many interesting objects to be mounted dry. When this mode of preservation is used, it is necessary that all the sea-salt be thoroughly washed

from them. As they are, however, most frequently mounted in balsam or liquid, they will be more fully noticed in other places.

The scales of fishes are generally mounted dry when used as ordinary objects; but for polarized light, balsam or liquid must be used, as noticed in Chapter IV. To mount a fish-scale, however, in a satisfactory manner, care must be taken that it is perfectly clean. This can be accomplished only by careful washing, in which process soft camel-hair pencils will often be useful. When the slime or mucus has once dried, it is very difficult to remove. The variety and beauty of these are quite surprising to the novice. It is also very interesting to procure the skin of the fish when possible, and mount it on a separate slide to show how the scales are arranged. The sole is one of the most unusual forms, the projecting end of each scale being covered with spines, which radiate from a common centre, while those at the extremity are carried out somewhat resembling the rays of a star. One of the skates has a spine projecting from the centre of each scale, which is a very curious opaque object, especially when the skin is mounted in the manner described. The perch, roach, minnow, and others of the common fishes give the student good objects for his cabinet, and may be procured without difficulty. The scale of the turbot is a splendid object for the polariscope when mounted in balsam.

Insects which are very transparent, or have the "metallic lustre" with which any medium would interfere, are mounted dry. The diamond-beetle, before mentioned, is a splendid example of this; the back is generally used, but the legs, showing the curious feet, are very interesting objects. Indeed, amongst the legs and feet of insects there is a wide field of interest. When they are of a horny nature, it is best to dry them in any form preferred, but to use no pressure; when, however, they are wanted flat, so as to show the feet, &c., extended, they must be dried with a gentle pressure betwixt blotting-paper if possible. But this will be treated more fully in Chapter IV.

The eyes of insects are sometimes allowed to dry in their natural shape, and mounted as opaque objects; but generally they are used as transparencies in balsam or liquid, so the description of the treatment which they require will be deferred to Chapter IV.

Hairs when not too dark, are sometimes transparent enough when mounted dry, but are usually mounted in balsam. These will be more fully noticed in another place, but there are some without which no cabinet is deemed in anywise complete. Many different species of bats, English and foreign, present us with hairs the form of which we should never have dared to imagine without microscopic aid. Other curious objects are found in the antennæ of crabs. You can also readily know whether you are being deceived when you buy what you deem a real sealskin or sable. From some of the common caterpillars I have obtained exquisitely beautiful slides, and a kangaroo is a true friend to an object-gatherer.

The hair of the ornithorhynchus is a very curious object, having a thin place in the middle of its length, and so presenting somewhat the appearance of a flail.

These are a few of the objects which are often mounted dry, but some of them should be shown in balsam or liquid also, and there is much difference of opinion as to the best way of preserving others. This, however, is explained by the fact, that the transparency which balsam gives, interferes with one property of the object, and yet develops another which would have remained invisible if preserved dry. The only method of overcoming this difficulty is to keep the object mounted in both ways, which is comparatively little trouble.

I may here mention that many prefer the lieberkuhn for the illumination of opaque objects; and a good background is gained by putting upon the under-side of the slide, immediately beneath the object, a spot of black varnish, which does not interfere materially with the light.

CHAPTER IV.

MOUNTING IN CANADA BALSAM.

THE nature and use of this substance has been before spoken of, so that the method of working with it may be at once described.

Perfect dryness of the objects is, if possible, more necessary in this mode of mounting than any other, as dampness remaining in the object will assuredly cause a cloudiness to make its appearance in a short time after it is fixed. Where pressure does not injure the specimens, they are most successfully treated when first dried betwixt the leaves of a book, or in any other way which may prove most convenient, as noticed in Chapter III.

Before describing the methods of proceeding with particular objects, general rules may be given which should be observed in order to succeed in this branch of mounting.

As the object is to be thoroughly immersed in the balsam, it is evident that when it has once been covered, so it must remain, unless we again free it by a process hereafter mentioned, which is very troublesome; and on this account there must be nothing whatever in the balsam except the object. The inexperienced may think this an unnecessary caution; but the greatest difficulty he will meet with is to get rid of minute bubbles of air, perhaps invisible to the naked eye, which appear like small globules when under the microscope, and render the slide unsightly, or even worthless. Balsam dissolved in benzole will be found invaluable in mounting without air-bubbles; if a few are left in the specimen, by the next morning they will have entirely disappeared. In making this solution the balsam should be first boiled gently till on dropping a small quantity into water it is