File:The Civil engineer and architect's journal, scientific and railway gazette (1839) (20627745096).jpg

Title: The Civil engineer and architect's journal, scientific and railway gazette
Identifier: civilengineerarc06lond (find matches)
Year: 1839 (1830s)
Authors:
Subjects: Architecture; Civil engineering; Science
Publisher: London : (William Laxton)
Contributing Library: Northeastern University, Snell Library
Digitizing Sponsor: Northeastern University, Snell Library

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1842) THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 69 am informed, by the passengers in the steam boats. All were excitedâall â were delighted at the Success of the experiment, and congratulation upon congratulation flowed in upon Mr. CuUtt for the magnificent manner in which he had carried his project into execution. As a proof of the easy, graceful, and swimming style with which Round Down Cliff, under the gentle force and irresistible influence of Plulus and Pluto combined, curlseyed down to meet the reluctant embraces of astonished Neptune, 1 need only mention that the flagstaff, which was standing on the summit of the cliff before the explosion took place, de- scended uninjured with the fallen debris. No fossil remains of the slightest importance were brought to light, which was a matter of disappointment to many. A very few even of the most Ordinary character were found among the mass, which it may well be imagined was soon after the explosion, teeming- with the curious multitude from the cliffs above anxious to obtain some relic of the event. On examining the position occupied by the debris of the overthrown cliff, we were much pleased to find it more favourably disposed than we could have conceived possible. Instead of occupying the site of the proposed railway at the foot of the cliff, it had by its acquired velocity slid past it. and left comparatively little indeed to be removed. At some considerable distance from the cliff, the fragments appeared to be heaved up into a ridge, higher than any other part, forming a small valley towards the cliff, and another seaward, beyond which a second ridge appeared, when it finally slopes of! towards the sea. The chalk was by no means hard, and appeared thoroughly saturated with water. The great bulk of the fragments ranged from about 2 to perhaps 8 or ten cubic feet, although we observed a vast number of blocks, which contained from two to three cubic yards and up- wards, one of which was driven some distance into the Shakespeare Tunnel, without doing injury to the brickwork. There was very little, indeed, of what might be termed rubbish in the mass. Previous to the explosion, we had heard it stated that about a million yards were expected to be detached ; indeed the Railway Times so stated it, on the 21st ultimo, apparently from authority, and after the explosi n took place, it was publicly asserted by one of the officials, that three quarters of a million of cubic yards had come down. Now, on cubing the stated dimen- sions of the mass, which were given as under 300 feet in height by, say 50 feet longer than ihe gallery, which would therefore be 350 feet, by an average thickness or depth from the face of the cliff of 60, we shall have 233,333 cubic yards ; but as the present face slope of the cliff is greater than before, the average thickness perhaps might be increased to 75 feet, which would make the quantity 291,686 cubic yards, from this is to be deducted 50,000 yards, the estimated quantity to be now shifted in forming the road, we shall then have 30,000 yards effectively removed by the expenditure of one ton of powder. We understand that Mr. Cubitt, the engineer, afterwards stated that a saving of six months' work, and £7000 expenditure was effected by this blast. Now allowing Sd. per yard for the removal of the quantity now required to be shifted, which would amount to £1250, and £500 for the powder used in the blast, the cost of forming the galleries, tamping, &c. &c, we shall find that this mass has been removed at a cost of 1.44 pence per yard. Again, taking Mr. Cubitt's statement, that a saving has been effected of £7000. to which, if we add the £1750, expenditure by the present plan, we shall find that he estimated the cost of removal by hand labour, at rather less than ~l\d. per yard. We felt an interest in examining the beds and fissures of the chalk in the neighbourhood of this blast, which clearly indicated that the plan of removal adopted by Mr.'Cubitt, was not only the cheapest, but the safest method which could have been adopted. The vertical fissures which here traverse the chalk appear to lie pretty nearly parallel, and at a slope perhaps of one-fifth to one-tenth to one. It was in one of these fissures that the whole mass parted and slipped down, on which we believe it had set pre- viously, no doubt brought about by the infiltration of water more than the sapping of the base by Ihe sea. So treacherous indeed was this chalk, that if we are rightly informed, a mass equal nearly in bulk to that blasted on Thursday came down unexpectedly some time since in the night time, burying in its ruins a watchman or foreman belonging to that part of the line. In the zigzig gangways cut along the face of the cliff, to enable persons to ascend to the summitâthis sliding of the chalk where those vertical fissures are intersected, appears very frequently, inspiring the passer-by with a feeling of great insecurity. How far the water might be intercepted, or otherwise be prevented from filtering through these fissures is a question of great importance, and would not, we think, be one of difficult remedy. It also becomes a matter of interesting inquiry as to the effect which a lesser qantity of 'powder would have had, deposited and fired in the same manner. Would it only have made the mass insecure, or caused a partial sliding down, rendering it then more difficult of removal by hand than at first ? The proportion of powder which Mr. Cubitt employs in his blasting operations we understand is determined thus : " The cube of the line of least resistance in feet, gives the quantity in half ounces j" but in this case there does not appear to have been any such quantity employed, though much more than heretofore is found necessary in usual blasting ope- rations. Perhaps the most curious circumstance, connected with the operation, was the apparent absence of shock on the firing of the charge on some spots in the immediate vicinity, while at other, far more distant, it was clearly perceptible. Thus where the batteries were placed, those in charge of them thought the charge had missed fire, from their being insen- sible to any shock, while at five times the distance along the face of the cliff, it was clearly felt. But even along the face of the clill it was very evident that the shock was felt by some and not by others, though standing within a few yards of each other.) Fig. 1.âSection of the Cliff.
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Fig. 2.âSection showing the movement of the mass.

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