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 The most useful cheap instrument I know is Field's School Microscope, a very compact little instrument having three simple lenses which, separate or combined, give a magnifying power of from five to forty diameters. This, with the simple lenses, live box, needle, and other appliances, costs 10s. 6d.; a compound body may be added for 2s. 6d. extra. This will give powers of from twenty to eighty diameters. It is well to have this compound body at first, us the cabinet is then made of sufficient size to hold the compound body and all the other apparatus. For an additional 2s. 6d. a Wollaston doublet may be added; and, as this lens is a combination of plane-convex lenses placed in such a manner and of such a focus as to reduce chromatic and spherical aberrations, for 15s. 6d. it is possible to possess a microscope nearly achromatic, giving a power of 120 diameters, which is sufficient for almost all the work which the young botanist will have to do. All my own earliest work in mosses was done with this instrument, and I believe I learned more by its aid than I have over done with the more expensive instruments I have since used. As a simple microscope it will always be useful for dissecting and mounting purposes, and I can say with confidence that the student who has acquired all the knowledge of structure that this cheap little instrument will place within his reach will have gained such an insight into the moss world as will enable him to determine with a little patience the most difficult of mosses. 



It was upon one of the few fine mornings at the end of August that I stood upon the edge of the high land overlooking the Vale of Hope, and looked down upon Castleton. Before me, in the far-off distance, were the hills in the direction of Sheffield that appeared to form the eastward termination of the vale, while on my left appeared the sharp peak of Win Hill, the more rounded summit of Lose Hill, and, very close to me, the precipitous side of Mam Tor, of which more anon. Then on my right were seen the road gradually winding up the hill-aide to Tideswell, the grey ruins of the ancient stronghold of the Peverils, and the bleak moors which characterise that part of Derbyshire.

The exact spot whore I stood to view the Vale of Hope was a remarkable one. It was just on the edge of the great plateau of mountain limestone. Behind me stretched that formation, before me lay the Yoredale Rocks overlying the same. These rocks, which take their name from the valley of the Yore, or Ure, in Yorkshire, where they are most fully developed, are beautifully exposed in the steep escarpment of Mam Tor, or the Shivering Mountain. Here they will be seen to consist of alternate layers of sandstone and shale—the latter being impregnated with oxide 