TABLE II.-Examination of the Densities of Sodium-Hydroxide Solutions by the Graphic Method.

Apparent errors of the experimental points expressed in terms of the density x 106. Mean experimental error

= 6.31.

A. Apparent errors according to a drawing showing breaks at 3 to 4, 12·1, 20·0, 24-05, 29-40, 350, 38·77, and 42.6 per cent.

B. Apparent errors according to a drawing showing breaks at 1·8, 7-8, 16, 22, 26-7, 32-2, 36·9, 40·7, and 46·4 per cent.

C. Apparent errors according to a drawing showing breaks at 12·1, 24-05, 35, and 42.6 per cent.

D. Apparent errors according to a drawing showing breaks at 3-5, 200, 29′4, and 38.77 per cent.

TABLE III.-First Differences of the Densities of SodiumHydroxide Solutions at 15°.

TABLE IV.-Densities of Sodium-Hydroxide Solutions at 15°.

Phil. Mag. S. 5. Vol. 37. No. 227. April 1894.

20

TABLE V.-Densities of Solutions of Potassium Hydroxide at 15°.

45 8744 1467072
44.9641 1.456586 1.455392
440859 1446491 1.445305
43-2403 1.436825 1.435647
42.4866 1.428221 1:427050
41.6367 1.418573 1:417410
40.9866 1.411285 1-410128
40-0774 1-401056 1:399906
39.2581 1-391941 1:390799
38.4660 1:383093 1.381959
37.6370 1:373975 1:372848
36.7947 1:364675 1:363556
36.0522 1:356553 1.355440
35.1445 1.346618 1.345513
34-4019 1:338584 1:337486
33.2745 1.326436 1.325349
32:0207 1.312941 1:311864
29.8776 1-290240 1.289182
28.1861 1-272532 1.271487
26.1460 1.251426 1-250400
24-5136 1.234723 1.233710
22.1249 1.210596 1:209604
20-2729 1.192183 1.191205
18-2119 1.171777 1.170817

1.465868

TABLE VI.-Densities of Solutions of Potassium Hydroxide

at 15°.

XXXIII. "Densities in the Earth's Crust."

By Rev. O. FISHER, M.A., F.G.S.*

N a letter which appears under the above heading in the

February Magazine,

expresses a wish that I would either admit or deny the value of Professor Blake's criticism † upon my conclusions concerning the comparative densities and thicknesses of the layers of the earth's crust beneath the oceans and continents respectively.

I do not feel much doubt about the correctness of my work upon this subject, because it was under very careful consideration for several weeks, not only by myself but also by Mr. Brill, whose mathematical ability is unquestionable; and I think Mr. Blake has thrown it aside as unworthy of his consideration rather too hastily. If he had more fully mastered my results, he would not have stated in his first paragraph that "the argument about the underlying layers of the crust seems to depend on the greater density of the superficial layer in continental than in oceanic areas"-which is the exact opposite to the conclusion at which I have

*Communicated by the Author.

† 'Annals of British Geology,' 1892. Introductory review.