_Natrolite_.--The finest specimens of this mineral that have ever been found in Bergen Hill were taken from a bed of it in this tunnel, having in its original form, before it was cut out by the tunnel passing through, over one hundred square feet, and from one-half to two and a half and even three inches in thickness; it was in all possible shapes and forms--all extremely rare and beautiful. A large part of one end of this bed still remains, and, by careful cutting, fine masses may be obtained. This bed may be readily found; it is nearly horizontal, and in its center about four feet from the floor of the tunnel, and about half an inch thick. It is down Shaft No. 2, on the north wall, and commences about eighty feet from the shaft. It is cut into in some places, but there is plenty more left, and can be obtained by cutting the rock above it and easing it out by means of the blade of a knife or similar instrument. This natrolite is a grouping of very small but perfect crystals, having the forms shown in Fig. 5; they are from a quarter to an inch long, and, if not perfectly transparent, are of a pure white color; they may be readily recognized by their form, and occurring in this bed. Its hardness, which is seldom to be ascertained owing to the delicacy of the crystals, is about 5, and the specific gravity 2.2. This is readily found, but is no distinction; its reaction before the blowpipe, however, is characteristic, it readily fusing to a transparent globule, clear and glassy, and by forming a jelly when heated with acids. The bed holding the upright crystals is also natrolite in confused matted masses. This mineral has also been found in other parts of the shaft, but only in small druses. There is a prospect at present that another bed will be uncovered soon, and some more fine specimens to be easily obtained.