on the leaves of the book they are reading, the heat from which, if they are near sighted, inflames the cornea, and hastens, I verily believe, the approach of cataract. Another cause of this disease is the protracted hours these females are made to work, who are connected with dress-making. But to return to my object, which is to propose a remedy, hitherto unthought of; I mean, by tapping the crystalline instead of removing it altogether with its capsule; and this, I think, might be effected, since Mr. Stephenson has proved to the world, that there is no danger in penetrating, with his new-invented lancet, into the interior of the crystalline portion of the eye. I would therefore propose, as an improvement on his discovery, that after making an incision of a certain proportion, by means of an instrument like his, a small delicate tube should be introduced, of a size proportioned to the incision, one end of which should penetrate to the crystalline humour, so as to allow the operator to extract through the tube all that foul suffusion which we call cataract, in order to enable the crystalline capsule to be replenished with a purer fluid. In a matter of such great importance, I trust you will not refuse to convey my ideas on this subject, although no medical man, when you recollect, as I believe was the case, that the stomach pump originated with the carpenter of St. Thomas's Hospital.

I remain, yours, &c.

GEORGE CUMBERLAND, SEN.

Bristol, May 10, 1844.

ATMOSPHERIC MARINE ENGINES-THE "" "SAPPHIRE.

Sir, The objections of your correspondent "S." to my views, upon the subject of friction, would have been quite correct if I had been discussing the comparative friction of engines of different pressure, and the same construction; but they are not so, as I referred to those of different construction and the same pressure. The friction of a piston is proportional to its area multiplied by the highest pressure, while the power is proportional to its area multiplied by the mean pressure of the steam and vacuum.

In the atmospheric engine the pressure varies; in the double-acting, it is constant. The friction of the piston in the former must therefore be greater in proportion to the power, than it is in the latter.

However, both this additional friction and loss of heat which "S." fears, and which must, if a proper system of felting be adopted, be extremely slight, are more than counterbalanced by the advantages of atmospheric engines in other respects. I cannot see why these engines should be named after Mr. Watt, merely because his condensers are used in them as well as in all other condensing engines of the present day.

I should have thought it more appropriate to name them after the late Mr. Samuel Seaward, who has united the engine of Newcomen and Smeaton to the improvements of Watt, and our modern engineers. I am, Sir, Yours sincerely,

CURVE.

DR. CLANNY'S SAFETY LAMP. At the last monthly meeting of the Literary and Philosophical Society of Newcastleon-Tyne, Dr. Glover read a paper exhibiting the latest improvements effected in Dr. Clanny's Safety Lamp. He commenced by describing the original lamp of Dr. Clanny, which, although safe, was too cumbrous for general use. He then adverted to the lamp invented by Stephenson, who, he said, had undoubtedly made the discovery that explosion will not pass through very small apertures, previous to the researches of Sir Humphry Davy. But, although, to the former gentleman the idea had occurred that air might be admitted through apertures smaller than would permit flame to pass, yet he had not arrived at this conclusion by a series of skilful, philosophical investigations, as had been the case with Sir Humphry Davy. Dr. Glover then pointed out defects in the Davy Lamp, which render its appellation of "Safety Lamp" not altogether correct. The wire gauze may be compared to an immense multitude of very short tubes, of small diameter, placed side by side, through which air and light will pass, but through which flame will not pass. It is necessary to prevent the passage of flame through a small tube, that the length of the tube should be considerable in proportion to its diameter. If, therefore, the meshes of the gauze be too coarse, then flame will pass; also, gauze which will be perfectly safe in explosive mixtures in a state of rest, will cease to be so when either the lamp or the mixture is in rapid motion. In constructing a lamp for coal mines, we must make it so that, while it is safe, it will also transmit a sufficient quantity of light. Now it happened, Dr. Glover continued, that in constructing lamps of wire gauze, those two conditions were incompatible. Sir Humphry

Davy's principle was undoubtedly correct, for the aperture in wire gauze can be made so fine that flame will not pass through, but in such a lamp the light transmitted is too feeble to be of any use. It, therefore, happened, that to allow light enough to pass, the meshes of the Davy Lamp were obliged to be made so large as to allow flame, under some circumstances, to pass. After stating the defects of the Davy lamp, Dr. Glover proceeded to consider the various attempts which had been made to remedy them. He briefly referred to the alterations of Clanny, Upton, and Roberts, Stephenson, and Museler, of Belgium, and he gave the preference in every respect to the latest lamp of Dr. Clanny. In this lamp the air is admitted by a wire gauze cylinder, through which the products of combustion also escape. The flame is encircled first by a tube of mica, and then by one of glass, which latter is protected by a brass cage. The great principle in this lamp is, the admission of air to the flame wholly from above. By this means, the influence of currents, acting laterally, is in a great measure prevented, and the light being transmitted through glass, the wire gauze can be made of that degree of fineness which will ensure its being safe.-The Newcastle Chronicle.

DR. URE'S ALKALIMETER AND ACIDIMETER.

In

In constructing (1814) the Alkalimeter, I availed myself of the lights recently shed on chemical proportions by Dr. Dalton's atomic theory, and I thus made it to represent, not relative, but absolute measures of the amount of real alkali existing in any commercial sample. The test-liquor used at that time was sulphuric acid, which is most readily and accurately diluted to the requisite degree by means of a glass bead, very carefully made, of the specific gravity that the standard acid should have. order to make the test-liquor, therefore, nothing more is requisite than to put the bead into distilled water, and to add to it somewhat dilute but pure sulphuric acid, slowly and with agitation, till the bead rises from the bottom, and floats in the middle of the liquor at the temperature of 60° Fahr. The delicacy of this means of adjustment is so great, that a single degree of increase of heat will cause the bead to sink to the bottom-a precision which no hydrometer can rival. The test-tube, about 14 inches long, contains generally 1000 grains of water, and is graduated into 100 equal parts by means of equal measures of mercury. The test-liquor is faintly tinged with

335

red-cabbage or litmus; so that the change of colour, as it approaches to the saturating pitch, on adding it to 100 grains of the commercial alkali, becomes a sure guide in conducting the experiment to a successful issue. One hundred measures of this testliquor neutralize exactly 100 grains of absolute soda (oxide of sodium), and of course very nearly 150 of potash. A bead may also be adjusted for test-liquors, of which 1000 grain measures neutralize 100 of potash, and therefore 66% of soda, as well as other proportions, for special purposes of greater minuteness of research. One may be so graduated as to indicate clearly a difference of one-hundredth of a grain of ammonia. In making such nice experiments it is, of course, requisite to free the alkaline matter beforehand from sulphurets, sulphites, and hyposulphites, by igniting it in contact with chlorate of potash, as long since recommended by Guy Lussac. With such means in careful hands, all the problems of alkalimetry may be accurately solved by an ordinary operation.

On the same principle my Acidimeter is constructed; pure water of ammonia is made of such a standard strength by an adjusted glass bead, as that 1000 grain measures of it neutralize exactly a quantity of any one real acid, denoted by its atomic weight upon either the hydrogen or oxygen scale or radix; as, for example, 40 grains of sulphuric acid. Hence it becomes a universal acidimeter; after the neutralization of 10 or 100 grains of any acid, as denoted by the well-defined colour in the litmus-tinted ammonia, the test-tube measures of ammonia expended being multiplied by the atomic weight of the acid, the product denotes the quantity of it present in 10 or 100 grains. The propor tion of any one free acid in any substance may thus be determined with precision, or to one-fiftieth of a grain, in the course of five minutes. Like methods are applied to Chlorometry, and other analytical purposes, with equal facility; adapting the test-liquor to the particular object in view. Instead of using beads for preparing the alkalimetric and acidimetric test liquors, specific gravity bottles or hydrometers may, of course, be employed; but they furnish incomparably more tedious, and less delicate means of adjustment. To adapt the above methods to the French weights and measures, now used generally also by the German chemists, we need only substitute 100 deci-grammes for 100 grains, and proceed in the graduation, &c., as already described.

The possession of two reciprocal testliquids affords ready and rigid means of verification. For microscopic analyses of alkaline and acid matter, a graduated tube

of small bore, mounted in a frame with a valve apparatus at top, so as to let fall drops of any size, and at any interval, is desirable; and such I have employed for many years. Of this kind is my ammonia-meter, used in the ultimate analysis of guanos and other azotized products, in conjunction with a modified apparatus on the principle of that of Varrentrapp and Will. It may be remarked, that when the crude alkali contains some hyposulphite, it should not be calcined with chlorate of potash, because one atom of hyposulphurous acid is thereby converted into two atoms of sulphuric, which of course saturate double the quantity of alkali, previously in combination with the hyposulphurous acid. In such cases it is preferable to change the condition of the sulphurets, sulphites, and hyposulphites, by adding a little neutral chromate of potash to the alkaline solution, whence result sulphate of chromium, water, and sulphur, three bodies which will not affect the accuracy of the above alkalimetrical process.-Lecture delivered by Dr. Ure before the Pharmaceutical Society.

NOTES AND NOTICES.

Adulteration of Exciseable Articles.-In consequence of the adulteration of various exciseable commodities having been carried on to a serious extent, the Commissioners of Excise have issued bills calling the attention of the public to the existing legal enactments on the subject, and notifying their intention to enforce the penalties upon manufacturers and dealers in every case in which they may be detected in infringing the law. For this purpose the several acts of parliament on the subject are quoted, and from these it appears that the articles are tobacco and snuff, beer, tea, coffee, chocolate and pepper, all of which, it seems, are frequently so seriously adulterated, or made up with other ingredients, as to defraud the revenue, and to cheat if not to poison the consumers. The following are the heads :-In manufacturing tobacco no other material or liquid is to be used than water, or water and salt, or alkaline salts only, or lime water in Welsh or Irish snuffs, under a penalty of 100%. In manufacturing tobacco water only, or in roll tobacco water and oil only, are to be used, under the same penalty. No person shall cut, grind, pound, colour, stain, dye, or manufacture any leaves, herbs, or plants, moss, weed, or wood, chicory, commings, or roots of malt, &c., to be mixed with tobacco and snuff so as to resemble them, under a penalty of two hundred pounds and the forfeiture of all tools and utensils used for that purpose. Beer and worts, it appears, are adulterated with molasses, honey, liquorice, vitriol, quassia, coculus indiæ, grains of paradise, Guinea pepper, opium, calx, &c., as a substitute for malt and hops. The penalty here is 100l. with forfeiture of the casks or vessels. The selling of these articles to any brewer renders the party liable to a fine of 5007., and the penalties extend to beer retailers. Adulterating tea with terra japonica, or any other drug or substance other than leaves of tea, 1007. Using in tea sloe leaves, liquorice leaves, leaves of tea that have been used, &c., or dying or colouring any leaves for that purpose, 107. Using burnt,

scorched, or roasted peas, beans, or other grain or vegetable substance to mix with or resemble coffee or cocoa 1007. Manufacturing substances in imitation of pepper, and mixing the same with pepper, penalty 1007.

Explosion of a Locomotive Boiler.-On the 1st inst., great alarm was created in the station yard of the Newcastle and Carlisle Railway, at the London road, near that city, by the explosion of the boiler of the "Adelaide" steam engine. The engine had just arrived with a train of empty coal wagons, and, having taken in a supply of coke, was about to start, when a terrific noise was heard, and the whole train enveloped in steam and smoke. On examination it was found that the upper part of the fire box had burst, and had lifted the engine from the rails to a distance of 18 inches, and striking the engine man, had thrown him backwards several yards. The stoker was thrown into the first coal wagon. When the engine man was discovered he was insensible, and though going on favourably, he cannot be pronounced out of danger. The stoker is rapidly recovering.-Carlisle Journal.

The Atmospheric Railway System.-At the last meeting of the Institution of Civil Engineers, Mr. Samuda gave the following estimate of the advantages to be derived from applying this system to a long line of railway. Taking for data the expenses on the London and Birmingham railway, which were stated to be per train per mile, for haulage, 15d.; ditto, for maintenance, 83d.; the cost of working the atmospheric apparatus would be-per train, per mile, for haulage, 5 55-100d.; ditto, for maintenance, 5 38-100d., with the additional advantage of travelling at a mean speed of 50 miles per hour, instead of between 20 and 25 miles per hour, with the locomotive system.

The Daguerreotype improved by Daguerre.-At the French Academy of Sciences, on the 22nd ult., a communication was made by M. Daguerre, relative to some improvements in the Daguerreotype process, chiefly for the purpose of taking portraits, the ordinary mode of preparing the plates not being found sufficient to enable the operator to obtain good impressions. The new substances of which M. Daguerre makes use are an aqueous solution of bichlorure of mercury, an aqueous solution of cyanure of mercury, oil of white petroleum, acidulated with nitric acid, and a solution of platina and chlorure of gold. The process is as follows:-the plate is po lished with sublimate and tripoli, and then red oxide of iron, until a fine black be obtained; it is now placed in the horizontal plane, and the solution of cyanure, previously made hot by the lamp, is poured over it. The mercury deposits itself, and forms a white coating. The plate is allowed to cool a little, and after having poured off the liquid, it is dried by the usual process of cotton and rouge. The white coating deposited by the mercury is now to be polished. With a ball (tampon) of cotton saturated with oil and rouge, this coating is rubbed just sufficiently for the plate to be of a fine black. This being done, the plate is again placed upon the horizontal plane, and the solution of gold and platina is poured over it. The plate is to be heated, and then left to cool, and the liquid having been poured off, the plate is dried by means of cotton and rouge. In doing this, care must be had that the plate be merely dried, not polished. On this metallic varnish M. Daguerre las succeeded in taking some very fine impressions of the human figure, which were exhibited.

INTENDING PATENTEES may be supplied gratis with Instructions, by application (post paid) to Messrs. Robertson and Co., 166, Fleet-street, by whom is kept the only COMPLETE REGISTRY OF PATENTS EXTANT from 1617 to the present time.

THE method of cleansing and sweetening casks, now commonly followed by brewers, distillers, and others, is to pass steam of a high temperature through them; but there are two serious objections to this method-first, it is extremely costly, the expenditure, on this account, amounting in some of our large breweries to many thousands of pounds annually; and, secondly, the wood imbibes from the steam a quantity of moisture which helps to reproduce those very fungous impurities which it is the special purpose of the

process to get rid of. From both these objections the new process, which we are about to describe, is entirely free. It is, comparatively speaking, cheap, and in respect of efficiency subject to no drawbacks. It consists principally in substituting for the steam, hot air-that is to say, in administering the heat, in which alone the purifying virtue rests, free from the moisture which accompanies it in the state of steam, and which is found to be productive of more harm than good-a very common-sense-like improvement, and one which, now it has been thought of, every one will (as usual) wonder was not thought of before, The only beneficial effect traceable to the administration of the heat in an aqueous form, is that the moisture helps to loosen and detach any solid matters which may collect on the inside of the casks; but it must be a rough crust indeed which a high degree of heat will not of itself cause to crack and peel off; and for very bad cases of the sort, Messrs. Davison and Symington have a most ingenious mechanical contrivance, which accomplishes more than could ever be effected by steam, in half the time.

Messrs. Davison and Symington describe their method as consisting, "firstly, in freeing the wood of casks and other like vessels, while they are in the course of being manufactured and in an unfinished state, from any injurious colouring or flavouring matters with which it may be impregnated, by exposing it to the action of rapid currents of hot air. Secondly, in freeing casks and other like vessels after they have been finished, and in use, from any mould, must, fungi, or

other like matters, which may collect on the inner surfaces thereof, partly by means of a machine or apparatus, which can be applied inside without removing the heads, partly by rinsing, and partly by causing rapid currents of hot air to pass through them."

The former of these methods is thus described by the patentees,

"First, As regards the casks and other like vessels, while they are in the course of being manufactured, or in an unfinished state. Instead of making them, as usual, of wood which has been dried or seasoned by long exposure to the atmosphere, and iş in that condition difficult to bend without blistering, we make use of wood in its new or green state, in which state it is formed into staves of the desired curvature and free from blister, with great facility. We then form,

or

'block off,' as it is called, the casks or other like vessels, by putting the staves and heads together, and binding them by temporary fastenings, and making due allowance for the shrinkage which afterwards takes place. We next subject these unfinished casks, vats, or other vessels to the action of a continuous and rapid current of heated air, until the wood has exhaled every particle (or nearly so) of its natural sap, or other aqueous particles with which it may have become impregnated. And this done, the casks are finally hooped and finished off in the usual way.

"The construction of the apparatus by which we produce the rapid current of heated air is represented in figs. 1, 2 and 3; fig. 1 being a sectional elevation; fig. 2 a plan, and fig. 3 a transverse section of the same. A is the furnace; a a a, are horizontal pipes which extend along the sides of the furnace, and b bb, pipes of a horse-shoe form, which rise vertically from the horizontal pipes and communicate therewith; c is a passage for the inlet to the horizontal pipes of atmospheric air from a fan-blower, or other impelling apparatus; d, a passage for the outlet of the heated air from the pipes, which is furnished with a sluice cock D, to prevent the steam, when used, from passing into the hot-air pipes, bbb; and e e e, nozzles through which the heated air rushes into the casks, or other like vessels. The arrows indicate the course which the air takes in passing to the nozzles."

The hot air, it will be observed, must