Science_, etc.--and thus find the part referred to, or by consulting other mineralogists who happen to know. Again, the person having found by inquiry that the part referred to is the Pennsylvania Railroad, and as this is fully a mile long and interspersed with various prominent looking, but veins of a mineral of little value, at any rate not the one in question, they are few who could suppose that it occurred in that. Apparently a vein of it would not be noticed at all from the surrounding rock of gravelly earth, but there it is, and in a vein of chlorite. This is so throughout the long and more or less complete stated lists of mineralogical localities. Thus I will, in describing the mineral, after explaining the conditions under which it occurs, give almost the exact spot where I have found the same mineral myself, and have left sufficiently fine specimens to carry away, and thus no time will be lost in going over fruitless ground, and further, this paper is written up to the date given at its end, insuring a necessary presence of them. In order that one not familiar with mineral specimens should not carry off from the various localities a variety of worthless stones, etc., which are frequently more or less attractive to an inexperienced eye, the following hints may be salutary. There are the varieties of three minerals, which are very commonly met with in greater or less abundance in mineralogical trips: they are of calcite, steatite, and quartz. They occur in so many modifications of form, color, and condition that one might speedily form a cabinet of these, if they were taken when met with, and imagine it to be of great value. The first of these is calcite. It occurs as marble, limestone; calcspar, dogtooth spar, nail head spar, stalactites, and a number of other forms, which are only valuable when occurring in perfect crystals or uniquely set upon the rock holding it. The calcspar is extremely abundant at Bergen Hill, where it might be mistaken for many of the other minerals which I describe as occurring there, and even in preference to them, to one's great chagrin upon arriving home and testing it, to find that it is nothing but calcite. In order to avoid this and distinguish this mineral on the field, it should be tested with a single drop of acid, which on coming in contact with it bubbles up or effervesces like soda water, seidlitz powder, etc., while it does not do so with any of the minerals occurring in the same locality. This acid is prepared for use as follows: about twenty drops of muriatic acid are procured from a druggist in a half-ounce bottle, which is then filled up with water and kept tightly corked. It is applied by taking a drop out on a wisp of broom or a small minim dropper, which may be obtained at the druggist's also. I do not say that in every case this mineral should be rejected, because it is frequently very beautiful and worthy of place in a cabinet, but should be kept only under the conditions mentioned