Laurence Holker Potts

Dr. L H Potts, M.D.

'Formation of Sub-marine and other Foundations by Pneumatic Power.— On Saturday evening se'nnight Dr. Ryan delivered a private lecture in the theatre of the Royal Polytechnic Institution, Regent- street, descriptive of Dr. Potts' discovery of the applicability of pneumatic power to the formation of foundations in bogs, mosses, or sands, in the construction of railways, bridges, docks, breakwaters, &c. He was assisted by Dr. Potts, who exhibited models of his apparatus, and conducted several interesting experiments, in illustration of the working of the system.

'Dr. Ryan commenced his lecture by remarking that Dr. Potts' attention had been first directed to the subject by a careful inspection of the beautiful structures built by the coral insect, and he had endeavoured to imitate nature by carrying out his system in detail. The tedious and laborious nature of the present process of pile-driving by means of the iron weight, technically termed a " monkey," which requires the employment of several men for some minutes to raise it to the falling point, even to obtain the result of a depression of a single inch, is well known; and the importance of the invention, if it can be successfully brought into practice, must be apparent to every one from the following description.

'The invention is mainly directed to the formation of sub-marine foundations, though it is equally applicable to the construction of every kind of erection, which has hitherto called for coffer dams, or required the aid of wooden piles. The main feature consists in the substitution of pneumatic power for manual labour, in the first process of driving the piles. Dr. Potts proposes to use hollow iron tubes as piles. The lower extremity of the pile is open, and it is placed in a vertical position upon the bank or other ground, whether composed of sand, mud, or other substance, miscible with or diffusible in water. To the upper extremity of the tube is affixed an air tight cap, with a flexible tube of jointed metal or elastic hose, termed the "proboscis," extending to a close receiver, from which the air is extracted by an air-pump, or by the condensation of steam or any of the other modes which will produce suction, the object being to remove the pressure of the atmosphere, and form a vacuum. When the air within the receiver, the connecting tube, and the pile, becomes sufficiently attenuated, a mixed body of sand or mud and water flows up through the pile into the receiver, and as often as the latter is filled with the mixed body so raised, the contents are discharged through a valve at the bottom. As the sand or mud is thus raised in the pile, the pressure of the atmosphere being removed from its interior, the pile descends by its own weight, and the external pressure of the atmosphere, the rapidity being necessarily proportioned to the degree of exhausting power applied, and the supply of water from beneath. The pile descends with considerable rapidity in loose materials such as sand and shingle, and provision is made for disturbing and bringing under its operation materials of greater tenacity and bulk, large boulders, for instance, and for supplying the water to serve for their temporary suspension in the current. A succession of tubes may be added to the first by means of screws, internal socket, flange or other joint, and the shape may be cylindrical, angular, or conical, according to the nature of the work, and they may be provided with external edges or wings so as to fit each other, and form a continuous line or wall of piles. In works where an insular or detached erection may be required, as in the commencement of a break-water or lighthouse, it is proposed to use an apparatus termed by the inventor a " syphunculus." Here he has again followed nature, by constructing this caissoon or syphunculus on the principle of that beautiful shell-fish the nautilus pompilius, which, having a variety of internal chambers, by letting the water in or out, can elevate or depress itself at pleasure. This caissoon having been made of the proper size, and the annulus divided into the several air-chambers, as in the nautilus, it can be floated to the proper place, and sunk by the gradual admission of water. The piles once sunk, Dr. Potts proposes to make a mass of concrete in the interior so as to form a firm and solid foundation for whatever kind of structure it is proposed to rear. This mass may be formed by the use of Roman cement, by the composition employed by General Pasley, by Medway mud, burnt up with lime, and by other substances described in the inventor's patent. This being mixed up with chalk, shingle, sand, or whatever other substance may be found convenient, a hydraulic pump is then employed for the purpose of binding them together, and forming one impenetrable mass. Dr. Potts has been several years engaged in investigating into the subject, and he is now naturally very sanguine of success. We understand the subject occupies the attention of the Commissioners for the construction of harbours of refuge round the coast, and the decision will be looked forward to with great interest. The lecture was attended by several scientific gentlemen, who seemed to entertain a good opinion as to the worth and practicability of the invention.'

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