As regards the latter, it is well to know that it is far easier to prevent the intrusion of small animal pests than it is to exterminate them after they have once found an entrance; and so, from the very commencement of the formation of the collection, all drawers and boxes should be charged with some substance that is objectionable, if not fatal, to them. Small lumps of naphthaline (albo-carbon) put into the various compartments, and renewed occasionally as they disappear by evaporation, will generally suffice to prevent the entrance of all pests, but this substance is not effectual as an insecticide for the purpose of killing them after they are in. Perhaps the best of all insecticides is the corrosive sublimate already mentioned, and this may be applied to any animal or vegetable object that is capable of providing food for museum pests, and it is difficult to find such an object on which they will not feed. Many of the specimens that find a place in a museum have been temporarily preserved in spirit previous to being dried, and if a little corrosive sublimate was dissolved in this spirit, the specimens will have been rendered perfectly free from all attacks of marauders, since the spirit will have saturated the whole object, carrying with it the dissolved poison. Most of the specimens that have not been treated by the above method would not suffer from a short immersion in spirit containing the corrosive sublimate; but in cases where it is considered inexpedient to do this, the same liquid may be applied to them by means of a soft brush. In this way even the dried botanical specimens may be rendered perfectly secure from attacks. CHAPTER VI _EXAMINATION OF MARINE OBJECTS--DISSECTION_ An enthusiastic observer of nature will learn much concerning the structure of natural objects with the unaided eye, but there are times when he will desire some kind of magnifier to reveal more perfectly the structure of minute parts, or to enable him to observe the small creatures that are invisible to the naked eye. Further, one may learn many interesting and instructive facts relating to animal and plant life by cutting sections for close examination, or by making such simple dissections as will enable one to observe the more salient features of internal structure; we therefore propose in the present chapter to make a few remarks and suggestions regarding work of this kind. A pocket magnifier is of great value to the young naturalist, both for the inspection of natural objects while engaged in out-door work, and for the subsequent examination of the specimens collected for study. It is often necessary to enable one to identify and classify small animals and plants, and will be in constant demand for the purpose of studying the less conspicuous external features. Such an instrument should be regarded as an essential companion of the naturalist, and should accompany him on every ramble.