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§ 6.-Water a conductor of Pulsation Signals. During the preceding series of experiments, I had ample proof of the great conducting power of water for this form of electrical impulse. Shocks or strange thrilling sensations were perceptible at every step while proceeding through the ground, as long as the morning continued damp. When, however, the sun became sufficiently powerful to dry up the dew, and remove the film of water from the wires, bamboos, and grass, then the wires alone conveyed the electricity. My experiments convince me that dry wood, earth, and masonry are perfect non-conductors of this kind of excitement. Even the bark of living trees seems a perfect insulator.
Some months previous to the experiments now described, I accidentally found too (by the falling of a wire into the large tank at the Medical College) that when water was available, only one insulated wire was requisite for completing communications. I did not omit the opportunity afforded by my experiments at the Gardens of following up this curious result, and although I find the fact has also attracted the attention of Professors Henry and Steinheils, these philosophers will, I feel convinced, learn with interest the simultaneous pursuit of the like object, in my humble investigations.
In one experiment the electro-magnetic machine was stationed at the ghât of Bishop's College, and one of its wires, but twenty-five feet long, dipped in the Hooghly at the ghât. The second wire ran along the dry path round through the Botanic Gardens, and terminated in Dr. Wallich's library. A wire led from the river at the ghât before Dr. Wallich's house, also into the library. The assistant stationed at the machine was directed to make the signals in the usual manner. Every signal told in the library without any notable diminution of effect.
It made no perceptible difference whether the tide was ebbing or flowing;-in several trials the damp mud even conveyed the signal unaltered in force or character.
The distance by water in the above experiment was 7,000 feet. In a second set of trials the machine was placed at Sir John Royd's garden, the water distance intervening being 9,700 feet, and with the same results as before. (See lithographed plan No. 1.)
In a third trial, seven miles of wire were disposed round the trees of the Garden, taking in its entire boundary-starting from Dr. Wallich's house and terminating in the river at Howrah ; a second wire was carried from the river, at the west end of the Garden (two miles
of the Hooghly being interposed) and proceeded to the north extremity of a nullah 3,000 feet in length; from the south end of the nullah a wire returned to the library. Thus we had altogether eleven miles of metallic and 13,256 feet of water circuit, the latter in two interruptions. The signal still passed as intelligibly and strongly as before. A lithographic plan is annexed in illustration of these details.
§ 7.—General remarks on the applicability of the preceding facts. I reserve for another occasion the description of several experiments which these facts led to, regarding the possibility of dispensing altogether with metallic conductors; and I now proceed to shew some practical circumstances, expenses, and other details regarding the application of these facts to the actual accomplishment of telegraphic correspondence.
To effect a perfect system of telegraphic communication for a distance, say of 500 miles, two wires are at most required; where a river passes between the termini, but one wire is necessary. If the water communication be the sea, the distance for which one wire will suffice will be at least quadrupled. Insulation of one wire is necessary. The wire may touch dry substances of any kind, but it must not come in contact with water or damp earth communicating with the second wire or with the river course.
Insulation according to my experiments is best accomplished by enclosing the wire (previously pitched) in a split ratan, and then paying the ratan round with tarred yarn-or the wire may, as in some experiments recently made by Colonel Pasley in Chatham, be surrounded by strands of tarred rope, and this by pitched yarn.
An insulated rope of this kind may be spread along a wet field, nay, even led through a river, and will still conduct without any appreciable loss the electrical signals above described.
In establishing a communication it would be advisable to bury the wire about two feet below the surface of the ground, in a narrow trench well rammed with pounded brick and mortar. At every ten miles the wire should rise through the ground in a masonry pillar, to allow of verification or of the discovery of the situation of accident. In India the Police Thannah houses might be conveniently used for this purpose.
The expense of copper wire per mile would be 272 rupees; of insulation 20; of trenching and masonry I can form no accurate estimate.
As no intermediate stations would be required, the expenses of establishment would be very trivial.
The cost of a magneto-electric machine of the maximum power would not exceed 207. The galvanic apparatus, constructed on the principle I described in 1837, would not at most cost 107. and would probably cost 51. per month for its constant support.
In Europe or America there exists no difficulty whatever to the adoption of this system of correspondence. In India unquestionably the obstacles are greater. Perhaps, however, on the other hand the very wildness of our jungle tracts would rather protect than endanger the buried wire. If properly laid down, in a few months none but those instructed, could find it. But wherever a railroad exists, there this method can be at once adopted. Indeed its applicability is so certain and infallible, its principles so simple, that I often wonder it has not been previously employed or even announced, and that the justly celebrated Mr. Wheatstone should have taken out a patent for a five-wired telegraph when every railroad in England already gives the required conductors.
The progress of science is hourly adding to the catalogue of triumphs effected by the sagacity of man over the seeming impossibilities of nature. Our own day has witnessed the miracle of gas illumination-the discovery of precious metals in potashes and in common salt-the extrication of the electric spark through the influence of magnetism-the solidification of carbonic acid-the fixing by the sun's light of the pictures it forms whether by shadow, reflection, or refraction. A conquest still greater than all which I have quoted would be the annihilation of time and space in the accomplishment of correspondence. That a signal can be passed between places 1,000 miles apart in less time than the motion of solar light through the firmament, is no less startling to assert than it is demonstrably and practically true.
ART. VII.-Extract from a Memoir on the Preparations of the Indian Hemp, or Gunjah, (Cannabis Indica) their effects on the Animal system in Health, and their utility in the Treatment of Tetanus and other Convulsive Diseases.-By W. B. O'SHAUGHNESSY, M. D. Professor in the Medical College of Calcutta, &c. &c.*
The narcotic effects of Hemp are popularly known in the south of Africa, South America, Turkey, Egypt, Asia Minor, India, and the adjacent territories of the Malays, Burmese, and Siamese. In all these countries Hemp is used in various forms, by the dissipated and depraved, as the ready agent of a pleasing intoxication. In the popular medicine of these nations, we find it extensively employed for a multitude of affections. But in western Europe its use either as a stimulant or as a remedy, is equally unknown. With the exception of the trial, as a frolic, of the Egyptian "Hasheesh," by a few youths in Marseilles, and of the clinical use of the wine of Hemp by Hahneman, as shewn in a subsequent extract, I have been unable to trace any notice of the employment of this drug in Europe.
Much difference of opinion exists on the question, whether the Hemp so abundant in Europe, even in high northern latitudes, is identical in specific characters with the Hemp of Asia Minor and India. The extraordinary symptoms produced by the latter depend on a resinous secretion with which it abounds, and which seems totally absent in the European kind. The closest physical resemblance or even identity exists between both plants-difference of climate seems to me more than sufficient to account for the absence of the resinous
Read before the Medical and Physical Society of Calcutta, on the 2d October,
We have extracted from this paper the sections relative to the popular uses and the effects on the animal system of these singular and valuable narcotics-for the professional details of cases, which we considered unsuited to our pages, we have to refer the reader to the Transactions of the Medical and Physical Society, current volume, fasciculus, for November, 1839.-EDS.