Although the produce of such a crop has not yet been clearly ascertained upon a large scale, the following may be taken as the estimate of one acre, from what has actually been produced in my experiment. Estimated value of the produce of one acre, 56 lb. opium, at 36s.... 36 bolls early potatoes, at 24s.......... 250 lb. of oil, cold drawn at 1s. 6d........ 125 lb. ditto warm, at 6d,...... 500 oil casks, at 18s. per 100,...... .....L.100 16 0 Expences, Opium costs the wholesale druggist in London at this time (May 1819) 17s. 6d. per lb., which, with a duty of Ss. 8d. per lb., makes it L. 1:6:6, and they charge the apothecaries 36s. per lb, lb, which is the present London price of the article. The London price of opium varies so much, that about twelve years ago, it was as high as 84s. per lb., and it seldom falls so low as 24s. If the crop can be got off the ground by the middle of August, it is proposed to have a second crop of potatoes or turnips, which will give, it is supposed, about L. 30 more. VOL. I. NO. 2. OCTOBER 1819. T Comparative View of the experiments of Messrs Ball, Howieson and Young, for ascertaining what quantity of Opium might be prepared in Britain. Mr Ball, from 576 square feet, or 1 fall and 28 square yards, obtained about......................... Ib. oz. dr. gr. per ...0 4 0 0 Dr Howison from about five falls, obtained.......0 8 4 0 In 1817, Mr Young, from 1 fall and 14 square yards, containing 1800 plants, obtained........ 0 4 0 0 According to Mr Ball's method, 1 fall produced 2 ounces and 2 drachms, or........ .22 8 0 0 According to Dr Howison's method, 1 fall pro duced 1 ounce 5 drachms, and 36 grains, or 17 0 0 0 By Mr Young's method, 1 fall produced 2 ounces 7 drachms 2 grains and, or......... 28 12 6 24 In 1818, Mr Young, from 1 fall obtained 5 ounces 6 drachms 4 grains and +, or....... 57 9 4 48 Explanation of the Figures. acre. Fig. 1. represents the skeleton of the poppy, and shows the anastomosis of the lactiferous vessels, ramified between the external and internal rind of the capsule. Fig. 2. represents a vertical section of the poppy. Fig. 4. represents the double longitudinal and oblique incisions upon the external rind of the poppy. Fig. 5. represents the poppy with the points of the star or capital cut off, and a thin slice of the external rind round it. Fig. 6. represents the double bladed convex edged knife, with a brush at one end for gathering the milky juice. The blades at the other end are covered with a shield, except as much of the edge as is necessary for wounding the external rind of the capsule. The blades should be three inches long. Fig. 7. represents a tin flask, with a slip of tin across its mouth for scraping the brush upon, and for holding the milk. It should be six inches long, four broad, and one inch wide at the mouth *. EDINBURGH, May 1819. The Society of Arts have recently voted to Mr Young the Gold Isis Meda for his improved mode of collecting British Opium.-ED. ART. VII.—Account of a singular Affection of Vision. By JAMES RUSSELL, Esq. F.R.S. E. and Professor of Clinical Surgery in the University of Edinburgh. Contained in a Letter to Dr Brewster. As I know that you take a deep interest in every curious fact connected with optics, I use the freedom to send you an account of a singular affection of vision which occurred to me some years ago. A gentleman came to town for a consultation, on account of a severe complaint in his stomach. Previously to the commencement of this complaint, he saw equally well with both eyes, and the focal distance of distinct vision was the same in each of them. This distance, however, had now undergone a change in both eyes; and, what is a remarkable circumstance, the change in the two eyes was in opposite directions, the distance in the one eye having become longer, and in the other shorter, than the original focal distance. But while the two eyes no longer corresponded in their limits of distinct vision, each of them still retained the power of adapting itself to variations in the distance of external objects, so far as its limits of distinct vision admitted. The pupils retained their natural contractility to the stimulus of light. The cornea and the different humours possessed perfect transparency; and the most careful examination did not discover the slightest appearance of disease in any part of the eye. The gentleman' referred the origin of this affection of vision to the disordered state of his stomach, and I saw no reason to entertain the smallest doubt with regard to the justness of his conclusion. The eyes readily sympathise with any morbid irritation of the stomach, though it certainly would not have been expected, that one kind of irritation proceeding from the same source, should have produced such dissimilar effects in the two eyes. The gentleman left town before the complaint in his stomach was removed, which prevented us from verifying our opinion with regard to the dependence of the affection of his eyesight upon the state of his stomach by following the result of the case. The course of my reading has furnished me with only a single case at all analogous to the one above related. It is given upon the authority of Mr Ware*, "who was consulted by a lady on account of a recent discovery that she was unable to read with the left eye. She held the book at an unusual distance, which was the more remarkable, as she had previously been short-sighted." The interposition of a convex glass of thirty-six inches focus removed all confusion. Upon taking a few medicines to remove some constitutional disturbance, the original focus of the left eye was restored. During all this time, the right eye continued short-sighted. I am, &c. EDINBURGH, 8th June 1819. JAMES RUSSELL. ART. VIII.-Account of the Earthquake which destroyed the Town of Caraccas on the 26th March 1812. By M. HUMBOLDT. THERE are few events in the physical world which are cal culated to excite so deep and permanent an interest as the earthquake which destroyed the town of Caraccas, and by which more than 20,000 persons perished, almost at the same instant, in the province of Venezuela. The general results of this frightful catastrophe have been long known in this country; but its particular details, so afflicting to human feelings, and the physical phenomena by which it was accompanied, so important in geological speculations, have been only recently described by M. Humboldt +. This distinguished traveller, who had visited the city of Caraccas previous to its destruction, has been at great pains to collect and compare the descriptions of individuals who had witnessed the effects of the earthquake, and has thus been enabled to draw a faithful picture of this terrible convulsion, marked with that glowing eloquence which characterises all his writings. We regret that our limits will not permit us to present our readers with all his reasonings respecting the influence of a system of volcanoes over a vast extent of cir Medico-Chirurgical Transactions, vol. v. p. 263. + Personal Narrative, vol. iv. p. 12. cumjacent country; but we may afterwards have another op-portunity of resuming this branch of the subject. 1 "The 26th of March was a remarkably hot day. The air. was calm, and the sky unclouded. It was Holy Thursday, and a great part of the population was assembled in the churches. Nothing seemed to presage the calamities of the day. At seven; minutes after four in the afternoon the first shock was felt; it was sufficiently powerful, to make the bells of the churches toll; it lasted five or six seconds, during which time, the ground was: in a continual undulating movement, and seemed to heave up like a boiling liquid. The danger was thought to be past, when a tremendous subterraneous noise was heard, resembling the rolling of thunder, but louder, and of longer continuance, than that heard within the tropics in time of storms. This noise pre-. ceded a perpendicular motion of three or four seconds, followed by an undulatory movement somewhat longer. The shocks were in opposite directions, from north to south, and from eastto west. Nothing could resist the movement from beneath upward, and undulations crossing each other. The town of Ca raccas was entirely overthrown. Between nine and ten thousand of the inhabitants were buried under the ruins of the houses and churches. The procession had not yet set out; but the crowd was so great in the churches, that nearly three or four thousand persons were crushed by the fall of their vaulted roofs. The explosion was stronger towards the north, in that part of the town situated nearest the mountain of Avila, and the Silla. The churches of la Trinidad and Alta Gracia, which where more than 150 feet high, and the naves of which were supported by pillars of twelve or fifteen feet diameter, left a mass of ruins scarcely exceeding five or six feet in elevation. The sinking of the ruins has been so considerable, that there now scarcely remain any vestiges of pillars or columns. The barracks, called El Quartel de San Carlos, situate farther north of the Church of the Trinity, on the road from the Cus-` tom-house de la Pastora, almost entirely disappeared. A regiment of troops of the line, that was assembled under arms, ready to join the procession, was, with the exception of a few men, buried under the ruins of this great edifice. Nine-tenths of the fine town of Caraccas were entirely destroyed. The |