wires from the opposite ends of the battery must then be thrust through the corks, as seen in the plate, and brought pretty nearly into contact. Immediately they come into this position, bubbles of air will be emitted from each wire. By the decomposition of the water, the oxygen gas is evolved at the positive, and hydrogen at the negative pole of the battery. It is not likely, however, that your correspondent will be satisfied, Mr. Editor, unless he collects the two gases in separate vessels. For this purpose he must provide himself with the two glass tubes, d and c, Fig. 2, open at one end and corked up at the other. He must fill them with water, and place them inverted in the glass, e, or some similar vessel, and must then pass the wires, a b, from the battery through the upper ends of each tube, and bring them nearly into contact at the bottom of the glass. The instant this is done, oxygen is disengaged at the end of one wire, and hydrogen at the other, and each rises in its own separate tube; and they are always found to be in proportion of two measures of hydrogen to one of oxygen. Before your correspondent makes this experiment, he should distil the water, to have it pure, or at least boil it, to separate the air and carbonic acid gas. I am, Sir, Your obedient servant, Milk-street, Cheapside, Aug. 2.

T. Z.

POISONING. IMPORTANCE OF CHEMICAL

KNOWLEDGE.

OUR readers will, most probably, have noticed the account of the trial of Wm. Jos. Hodgson, for administering poison to his wife, which took place on Wednesday, August 18th, at Durham. It has appeared in all the papers, and cannot have been read without having excited a painful interest. He is a medical man; his wife was unwell, and the medicines which the physician ordered were prepared for her under his direction. The

parties were only married in January 1823, and the marriage, at least on the lady's side, was one of affection. No motive appeared for the deed, as her whole fortune had previously been in his power; and he had settled 12001. on her for life, which was to revert to him at her death, in case she had a child. She had a child last Christmas, of whom the father was stated to be very fond; and his wife also described him as a kind husband. She was an unwilling witness, the prosecution, apparently, having been undertaken by her friends, who seem always to have been averse to the match; and she endeavoured to find an excuse for him, by stating him to be deranged. A physician had prescribed calomel and opium, on account of a rheumatic fever, and her husband administered the medicine. On Sunday evening, June 6th, his apprentice made up the medicine into a bolus, according to his directions, and carried it into the lady's room. From the testimony of her motherin-law, it appears, that he afterwards took the bolus down stairs, and returned with it. By his wife's desire, also, he divided the bolus into pills, and gave them to her. She immediately felt a heat in her stomach and throat, such as she had not before felt at taking similar pills, and complained of it. There was nobody present with her but her husband and a servant, and.. on her complaining he gave her a draught, after which she felt sick. Her mother, a Dr. Brown, a physician residing at Bishop Wearmouth, and Messrs. Gregory and Gregson, two surgeons, were then all sent for. The following is Dr.. Brown's description of the state of Mrs. Hodgson when he arrived, and of the steps taken subsequently to examine the contents of a phial chemically:

“I found Mrs. Hodgson very ill indeed; her pulse very quick and small; her skin was covered with a cold clammy sweat; there was a sense of burning in the throat that she complained of, extending along the gullet to the pit of the stomach,

There was vomiting at very short intervals; large quantities of mucus thrown up, and liquids that had apparently been given her. If a person had taken corrosive sublimate of mercury, I should conceive such symptoms would have been amongst the first that appeared. Having understood that the draught was given, I inquired after the composition of that draught. I think the patient herself told me the draught had been given. She said she began to vomit immediately after she took that draught. I observed to the prisoner, that I thought the symptoms were such as an over dose of tartar emetic would produce. Tartar emetic is in appearance like calomel; there is a difference between them, and a person of skill would easily discern it. I went down into the shop to see whether any mistake had occurred, but I found the tartar emetic and the calomel so situated, that I thought no mistake could have occurred. I think it is quite impossible corrosive sublimate could be mistaken for calomel; it is in crystals. A person could not use it in a bolus without first reducing it into powder. Corrosive sublimate of mercury could not be mistaken for powdered opium. They are so dissimilar in appearance, that I think it is impossible a person with a candle could mistake one for the other. In the dark, if a person pours it into a glass, as it is in crystals, they must be conscious of its not being powdered opium. To make a bolus it is necessary to mix the powder with a knife on the slab. Corrosive sublimate would grate or jar so much under a knife, as to render a person mixing it conscious of it. When I found that I could not clear up the mystery that seemed to exist, I ordered a draught to be prepared, of magnesia, 30 drops of tincture of opium, and some water. That was prepared in my presence by the prisoner. It was carried up stairs, and taken by Mrs. Hodgson, but it was immediately thrown up again. I then prescribed another draught for her, consisting of the

same quantity of tincture of opium, and two drachms of water. I was then in the bed-room. The prisoner went down to prepare it, and was absent for two or three minutes. On his return he had the apothecary's measure-glass in his hand, with the draught in it. The appearace of it was different from what I should have expected from my prescription. In the first place, it was more bulky. In consequence of that circumstance, I took the glass into my hand; it was also more turbid in appearance than it ought to have been; I tasted it.

Mr. Pollock-It never was administered to the prisoner's wife. Could, then, this evidence be received?

"Mr. Justice Bayley was of opinion that it could.

"The witness then proceeded. The liquid had a caustic metallic taste, and had such a taste as a draught containing corrosive sublimate of mercury would have. It had not the appearance which the crystals of corrosive sublimate of mercury dissolved in water would have. I was convinced that there was laudanum in it. Corrosive sublimate of mercury has no smell when dissolved in water; laudanum has. I think the smell of this draught was the same as it would have been if pure. On tasting the draught, I called for water to rinse my mouth, and ordered Mr. Gregory to be sent for. The phial was then given to Mr. Gregory, and was afterwards analyzed in my presence. Corrosive sublimate was found to be contained in it. The quantity, upon a fair calculation, was 13 11-14ths grains. That quantity, if not rejected by the stomach and met by antidotes, would be quite sufficient to destroy life. I should rather question whether three grains of it would destroy life. Upon discovering this draught, I required the white of eggs in water to be given; that is the antidote generally recommended by the highest authority. There is a little discrepancy on the question; but it is supposed that the white of eggs changes the corro

sive sublimate into calomel, and so makes it comparatively harmless. Previous to the giving of the white of eggs, none of the vomiting was saved; afterwards some of it was saved. After the white of eggs was given, it would be difficult to decide whether corrosive sublimate had been given, as it would be changed to calomel, and calomel had been given previously to Mrs. Hodgson. Some time after this draught had been given, Mr. Gregory, Mr. Gregson, the prisoner's father, the prisoner, and myself, went into the surgery. We examined the marble slab. We perceived the remains of a bolus, which we tasted. The taste was similar to that of the draught; it was that of corrosive sublimate. All the individuals present tasted it, the prisoner among the rest. They all said that it tasted of corrosive sublimate; the prisoner agreed with us as to the taste. I asked the prisoner to taste the draught, and also to taste the residuum on the slab. He did so; he agreed with me as to the taste of both. I was in his house from eleven o'clock at night till four the next morning. Something was said, that in case of Mrs. Hodgson's recovery, nothing was to be said about the transaction. I analyzed what came from Mrs. Hodgson's stomach; it amounted to nearly three pints. There was no precipitate of mercury in it. After the liquids she had taken, I did not expect to find any.

"Re-examined. One reason which I had for not expecting to find precipitate of mercury was, that so much had been thrown away before I thought of preserving the contents of the stomach; and the second reason was, the decomposition which corrosive sublimate suffers from the white of eggs would make any result obscure. Before I administered the white of eggs, I had not thought of preserving the vomitings. If the translation of gout or rheumatism had caused the symptoms which I observed in Mrs. Hodgson's stomach, I think that they would not

have been relieved by the application of the white of eggs. The white of eggs did relieve the symptoms in this case. I did not perform the analysis myself; I was present at it. The tests we applied to the liquid solution were carbonate of potash, lime-water, and ammonia. We made an amalgam; we reduced it back into such a substance as to be able to whiten gold with it.

"M. R. Gregory, a surgeon.-I saw a graduated measure-glass; I tasted it twice, and I said that I considered it to contain corrosive sublimate. Dr. Brown and Mr. Gregson, and the prisoner's father, went with me into the shop. We went to the slab, looked at it, and saw a place on which a bolus had been made. A very small quantity of matter still adhered to the slab. We scraped off a very small quantity. This was two hours after I had tasted the draught up stairs. I tasted it. The taste conveyed an impression to my mind that it was corrosive sublimate. It was the same with that of the draught. Mr. Ogden analyzed it. I saw it analyzed and submitted to the usual tests. [A paper produced.] That is my hand-writing. These are the notes of the analysis. The result of the experiment was, that the parties there were satisfied that the draught contained nearly 14 grains of corrosive sublimate. Mr. Barnard Ogden is in court. He was not examined, as he stated himself to be a Quaker, and had a scruple against taking an oath.

"Mr. Gregson, another surgeon, was called. He corroborated, in the leading points, the testimony of the two former medical witnesses, and added, that the prisoner pointed out where the bolus was made. The tests applied to the phial were, first, carbonate of potash, that produced a pale brickcoloured sediment; the second test was ammonia; the third, limewater. The sediment produced by the ammonia was a brownish white; and that produced by the limewater, a yellowish brown. The fourth test was a galvanic test, be

tween gold and zinc: the result was, gold whitened. The fifth test was by the tongue: result, styptic and metallic. There was on the slab sufficient of the composition left to be subjected to the galvanic test. I am not enough of a chemist to say whether, after we had all tasted it, there was enough to apply the tests of ammonia and lime-water. I consider the galvanic test infallible; in the test by the tongue one might possiby be mistaken. I have never made experiments myself, to know what the results of the experiments we made ought to be. I only know the results from my reading in chemistry.

"Dr. Brown examined by Mr. Brougham.-I was present at the application of these tests. I have experimented upon corrosive sublimate. Having done so, and know ing the tests which were applied to the liquid then produced, I should say that it was quite decisive as to the existence of corrosive sublimate. The effect of carbonate of potash would be to produce a precipitate of a brick-red. In this case the colour was a little affected by the laudanum with which it was mixed. If ammonia were applied as a test, the precipitate would be of a white colour; and if limewater, of a yellow colour. If the galvanic test were applied, gold would be whitened. I take that to be the surest test of all.

Cross-examined. That test would produce the same effect if it were applied to the submuriate of potash, the oxymuriate of potash, the red precipitate, or any other preparation of mercury: it would decompose the mixture, and whiten gold. It would give no criterion except that mercury was there, but not any criterion whether it was there as an active poison or a harmless ingredient. Corrosive sublimate is not the only preparation of mercury soluble in water: liquid nitrate is also soluble. The result of the experiments we made was altered by the presence of the laudanum. In à solution of corrosive sublimate, I certainly think that galvanism is

the best test that can be applied, as it shows the presence of a mercurial salt. Calomel is not in a state of chemical solution, and therefore cannot be suspended. If galvanism were applied as a test to a solution of corrosive sublimate, it would afford no certain test as to whether the liquid contained corrosive sublimate or liquid nitrate; but then it could be determined by either of the other three tests. I have mentioned lime-water, ammonia, and carbonate of potash. The taste of corrosive sublimate is very particular, and is quite distinct from that of all other mercurial salts with which I am acquainted. My mouth was so spoiled by tasting the corrosive sublimate that was in the phial, that I must speak with less confidence as to its existence in the residuum that was left upon the slab.

The prisoner was acquitted.There was only a presumption, arising from the symptoms, that the lady had taken corrosive sublimate; and this presumption was strengthened by the circumstance of the presented draught containing corrosive sublimate; but from the contents of the stomach having been thrown away, no proof could be come at that the woman had taken poison, and, consequently, none that poison had been administered. What struck us as remarkable in this case was, the ignorance of medical men: two of them knew nothing whatever of chemistry; a person performed the analysis under the direction of another, and neither of these was the medical man who had witnessed the transaction, nor was either of them examined. Of Dr. Brown's evidence, which to us appears deficient and incomplete,-of the analysis, which appears to have been unskilfully performed,-we shall hereafter have something to say. We have at present merely brought the case under the notice of our readers, to convince them of the necessity of acquiring accurate chemical knowledge, and to leave it open to ourselves to speak of it as it deserves, We have no de

sire to see human beings sacrificed to any theory whatever. We are not sorry that Mr. Hodgson was acquitted; for even supposing that he was guilty, his conscience will be punishment enough without any vindictive interference on the part of society; but it is of essential importance that the attention of medical men and young chemists should be directed to what can be proved by evidence on such occasions and what not, and that they, when called upon, should know how to enlighten a jury.

land. Another method of descending is to pass down the perpendicular shaft, through which the barrels, filled with salt, are brought to the surface. Towards the lower end of the rope a number of cross pieces of wood are firmly secured to it, the groups being separated from each other a distance of seven or eight feet. A couple of strangers seat themselves in this strange machine, clasping the rope in their arms, with their legs hanging down into the dark and deep abyss. They are then lowered till the next pair of cross sticks is on a level

LICZKA.

NEAR Cracow, in Poland, are the celebrated salt mines of Wieliczka; of them the following account has lately been given by a traveller :

"Notwithstanding the length of time during which these mines have been worked, and the quantity of salt taken out of them, their treasures appear to be as great as ever. They are situated in the outskirts of the Carpathians, a much finer range of hills to the eye than the Silesian mountains of the Giant, although they do not present, in this direction, any very elevated summits. The mines descend to the depth of about 1,500 feet, and though the miners go down on ladders by an ordinary shaft, the visitor has the accommodation of salt stairs, as ample and regular and convenient as if they had been constructed for palaces; and below the immense caverns, which have been formed by the removal of the salt, are, in many instances, connected with passages, equally smooth and spacious as the streets of a capital. The finest of them have been named after monarchs, because they have generally been, if not formed, yet widened into their present regularity and extent on the occasion of some imperial or royal visit. Thus you have Francis-street, and Alexander-street, and the great stair-case itself was originally hewn for the accommodation of Augustus III., of Saxony and Po

these a second couple is seated in the same way, and thus it goes on till the supply of visitors is exhausted or the rope is sufficiently loaded for its strength. The rope and its burthen are then allowed to drop slowly into the earth, the windlass above being stopped on a given signal as each party reaches the bottom, to give them time to dismount from their wooden horses. At the very end of the rope are two little boys with lights to afford the passengers the means of preventing the vibrations of the rope from dashing them against the walls of the shaft. Although not the securest mode of travelling, there is not much danger if care be taken (and the workmen are very attentive) to prevent the descent from being too rapid, for in this case, the rope immediately begins to twist, and the feeling be comes extremely unpleasant. You are landed below at the depth of 300 feet, in the first floor, near St. Anthony's chapel, an early production of the miners. The chapel itself, its pillars, with their capitals and cornices, its altar, and its images, are all hewn out in the salt rock. It is not true, however, as has often been stated, that the outlines of its different forms have retained their original accuracy, and its angles their sharpness. They have all suffered, as was to be expected from the long continued action of moisture, which is abundantly visible in every part of the chapel. The angles of the walls