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toadstone on either side of Salter’s Lane above Matlock Bridge ; 
at a height of more than 400 feet above the river Derwent. 
Here the burrows occur in great abundance. A specimen of 
these was exhibited; and the author contended that, from the 
shape and arrangement of the burrows, it was impossible that 
they could be the work of Pholades. The second case described 
was at the bottom of Miller’s Dale, in the upper part of a low 
cliff by the road side, about 12 feet above the present level of 
the river Wye. The author believed that this cliff was an 
artificial scarp formed in making the road. But even if the cliff 
were natural, he pointed out that Miller’s Dale was distinctly a 
valley of fluviatile erosion, that there was no indication of its 
having been submerged in its present form beneath the sea; 
and consequently that these burrows, so near the bottom of a 
gorge of this kind, could not be the work of any marine mollusc. 
He was therefore convinced that the Pholastheory was untenable; 
and believed that the burrows were excavated by Helices. 
May 16, 1870. 
The PRESIDENT (PROFESSOR CAYLEY) in the Chair. 
Communications made to the Society : 
(1) Helmholtz and Tyndall on the Theory of Musical 
Consonance. By Mr Sepury Taynor, M.A. 
[ Abstract. | 
The quality (‘timbre’) of musical sounds in general has been 
shewn by Helmholtz to depend on the relative intensity in 
which the partial tones, of which they consist, are present. 
Dissonance depends on the occurrence of beats between adjacent 
sounds. When two fundamental tones are so related to each 
other that beats are not produced between any well-developed 
pairs of the corresponding over-tones, the interval between the 
fundamental tones is consonant. 
