[Footnote 41: Compare De la Beche, _Geological Observer_, pp. 559, 560, and _North Derbyshire Memoir_, p. 123.] In some cases there is evidence of more than one outflow of lava in the same band of toadstone. Jukes believed that each band "was the result, not of one simultaneous ejection of igneous matter, but of several, proceeding from different foci uniting together to form one band," and he found that near Buxton, two solid beds of toadstone could be seen to have proceeded from opposite quarters towards each other without overlapping.[42] [Footnote 42: _Student's Manual of Geology_, 2d edit. (1862), p. 523.] In Millersdale the authors of the _Geological Survey Memoir on North Derbyshire_ observed that a band of toadstone about 100 feet thick showed six distinct divisions, which they were disposed to regard as marking so many separate beds.[43] In Tideswell Dale, on the west side of the valley, immediately to the south of the old toadstone quarry, two bands of toadstone are seen to be separated by a few yards of limestone. [Footnote 43: _Op. cit._ p. 19.] (_b_) Lavas with Tuffs.--It will probably be found that in many, if not in most cases, the outflow of lava was preceded, accompanied or followed by fragmental discharges. As far back as 1861, Jukes noticed that a toadstone band, about 50 feet thick, near Buxton consisted of two solid beds of lava "with beds of purple and green ash, greatly decomposed into clay, both above and below each bed and between the two."[44] [Footnote 44: _Op. cit._ p. 523.] [Illustration: Fig. 183.--Section at lime-kiln, south of Viaduct, Millersdale Station. ] An interesting section, showing this intercalation of the two kinds of material is exposed at the lime-kilns beyond the southern end of the railway viaduct at Millersdale Station. Over a mass of solid blue limestone (1 in Fig. 183) lies a band of bright yellow and brown clay (2), varying from six inches to two feet in thickness. This may be compared with the clay found above the limestone at Peak Forest (Fig. 181). But it is probably a layer of highly decomposed tuff. It is succeeded by a thin band of greenish limestone (3) containing an admixture of fine volcanic detritus, and partially cut out by an irregular bed, four to eight feet thick, of a highly slaggy, greenish, decomposing, spheroidal and amygdaloidal diabase (4). This unmistakable lava-sheet is followed by a bed of green granular tuff (5), which in some places reaches a thickness of three feet, but rapidly dies out. Over a space several yards in breadth, the succeeding strata are concealed, and the next visible rock is a dark, compact dolerite which weathers spheroidally (6).