1, birches; 2, willows; 3, beech; 4, potholes; 5, two waterfalls; 6, shallows, and vertical concave bank; 7, “Fairies’ Chapel”; 8, stratification of rocks; 9, mud deposits; 10, waterfall; 11, docks; 12, sloping trees; 17, weir; 14, railway viaduct; 15, horse chestnut; 16, aqueduct; 17, sycamore; 18, elm; 19, elm; 20, beech; 21, pond life; 22, well; 23, shale; 24, sycamore; 25, oak, bearing leaves in winter; 26, flagstones; 27, beeches, with wood-pigeons’ and magpies’ nests; 28, hawthorn hedge; 29, solitary oak; 30, gutter, with Pellia; 31, blackberry bush; 32, stunted oak. [Pg 394] Fig. 238.—Waterfall, Healey Dell, Rochdale (marked “10” in Fig. 237). Before the second journey each pupil should be provided with a blank sketch-map of the route. This may, in the first instance, be copied or traced from the six-inch Ordnance Map, and then duplicated in large numbers. Only the route and river, and a few of the more conspicuous landmarks, should be indicated on the maps as given to the class: details should be filled in, on the spot, by the pupils. The object of the second journey may conveniently be the study of the river and its work, and for this purpose it will be advisable to follow the stream in the direction of its flow. Variations in the speed of the current, and in the width of the stream and the hardness of the rocks or banks between which the water flows, should be noted, and the relations between cause and effect elicited by questioning. The hardness of the rocks at 4 has prevented the channel from being widened to a greater extent by the water, and accounts for the rapidity of the flow. A glass of water collected here is found to contain much suspended gravel. The considerable loss of weight of bodies in water is noteworthy, as explaining the great size of the stones which may be [Pg 395] transported by rivers. The scouring action of such stones is shown in the fine “potholes” at 4 and below the waterfall (Fig. 238) at 10, and has resulted also in the quaint stone portico of the “Fairies’ Chapel” under the right (west) bank of the river at 7. Again, the difference in the rates of erosion of hard and soft rocks has had much to do with forming the waterfalls at 5 and 10. Where the stream is wider and the flow slower (as at 6 and 9, and below 10), may be noticed sand and mud [Pg 396] deposits; and where the stream makes a bend it is found that the slowest flow and the maximum deposit are on the convex bank; while the concave bank is worn almost vertical (as at 6 and other places) by the swifter rush of the water, and may be undercut to such an extent as to cause the bank to give way. In this manner a river is constantly changing its course. The weir at 13, and the old water-wheel still to be seen in the ruined mill below, suggest remarks on the motive power of water, and on the circumstances which may cause the old industries