SCIENTIFIC SUMMARY. 
319 
versed, so that after passing through the hill-country between the Lake of 
Constance and Basel, the river flowed along an elevated plain formed of 
Miocene deposits, the remains of which still exist at the sides of the valley 
between Basel and Mainz. At the same time the Bhine flowed in a minor 
valley through the upland country formed of Devonian rocks, which now 
constitute the Taunus, the Hundsruck, and the highland lying towards 
Bonn, and by the ordinary erosive action of the great river the gorge was 
gradually formed and deepened to its present level. In proportion as the 
gorge deepened, the marly flat Miocene strata of the area between Mainz and 
Basel were also in great part worn away, leaving the existing plain, which 
presents a deceptive appearance of having once been occupied by a great 
lake. The paper gave rise to an important discussion. 
MECHANICS. 
The Transmission of Detonation by Tubes. — A valuable paper on various 
detonating substances was read by Mr. F. A. Abel, F.R.S., at an early meet- 
ing of the Royal Society. The author says that a great difference appeared, at 
first, to be established in the power possessed by tubes of different materials 
of favouring the transmission of detonation, the glass tubes being far in ad- 
vance of the others in this respect. It was eventually established very 
clearly, by a series of experiments, that this difference was not due, to any 
decisive extent, to the physical peculiarities (in regard to sonorosity, elasti- 
city, &c.) of the materials composing the tubes, but chiefly to differences in 
the degree of roughness of their inner surfaces, and in the consequent 
variation of the resistance opposed by those surfaces to the gas-wave. Thus 
the power of a glass tube to favour the transmission of detonation was 
reduced, by about two-thirds, by coating the inner surface with a film of 
French chalk, while the facility of transmission, through a brass tube, was 
nearly doubled by polishing its interior, and was increased threefold with a 
paper tube by coating the interior with glazed paper. The following are 
some of the points established by these experiments on the transmission of 
detonation by tubes : — 1. The distance to which detonation may be trans- 
mitted through the agency of a tube to a distinct mass of explosive sub- 
stance is regulated by the following conditions : — (a) By the nature and 
the quantity of the substance employed as the initiative detonator, and by 
the nature of the substance to be detonated, but not by the quantity of the 
latter, nor by the mechanical condition in which it is exposed by the action of 
the detonation. (b) By the relation which the diameter of the “detonator,” 
and of the charge to be detonated, bear to that of the tube employed, (c) 
By the strength of the material composing the tube, and the consequent 
resistance which it offers to the lateral transmission of the force developed 
at the instant of detonation, (d) By the amount of force expended in over- 
coming the friction between the gas and the sides of the tubes, or other 
impediments introduced into the latter, (e) By the degree of completeness of 
the channel, and by the positions assigned to the detonator and the charge 
to be detonated. 2. The nature (apart from strength or power to resist 
