Sections of some exquisitely beautiful objects are cut with much less trouble than the above. The Orbitolite, for instance, may be prepared in this manner. Take the object and by pressure with the finger rub the side upon a flat and smooth sharpening stone with water until the portion is reached which it is wished to show. The strength of the object will easily allow this to be accomplished with ordinary care. This side may then be attached to the glass slide with heated balsam, as above described, and the object may then be gently rubbed down to the degree of thinness required to show it to the best advantage. After removing all disengaged matter from the object by washing and thoroughly drying, it may be mounted in balsam in the usual manner, when it is equally beautiful as a transparent or opaque object. From this it will be seen that in many instances where a smooth stone is found sufficient for the work (which is often the case when the section is mounted in balsam) the final process of polishing advised above may be dispensed with, as in the Orbitolite, Nummulite, &c., &c. It is quite necessary that the stones on which the objects are rubbed be _perfectly flat_, otherwise one side must be acted upon before the other, and it will be found impossible to attain anything like uniformity. Where it is not practicable to cut a section and the object is very thick, a coarse stone may be first used to reduce it and the smoother afterwards. The consideration of the cutting of sections from shells would scarcely be deemed complete without some mention of what Dr. Carpenter terms the decalcifying process. Muriatic acid is diluted with twenty times its volume of water, and in this the shell is immersed. After a period, differing according to the thickness of the shell, the carbonate of lime will be dissolved away, and a peculiar membrane left, showing the structure of the shell very perfectly. This may be mounted dry, in balsam, or sometimes in liquid, according to the appearance of the object; but no rule can be given. The discretion of the student, however, will enable him to choose the most suitable method. From some shells it is easy to divide thin plates, or “laminæ,” which require nothing but mounting in Canada balsam to show the texture very well. In working, however, with those which are “pearly,” it will be found that experience and patience are needed, as they are very brittle and peculiarly hard; but a little practice will overcome these difficulties.