An improved method of etching metallic surfaces has been invented by Mr A. Piper of Wolverhampton. The metal surface is first of all coated with gold, silver, nickle, brass, or any other metal desired, in the ordinary electro-plating bath. The design is then drawn upon it in some resinous or other acid-resisting medium, and the metal is immersed in an acid, which eats away the coating, and at the same time produces a dead or frosted appearance upon the exposed metal beneath. The resinous drawing is now removed by any suitable medium which will dissolve it, leaving the design in relief upon a frosted ground. If desired, the operation can be reversed by leaving a groundwork of plated metal, while the design is bitten out by the acid.
A new stationary buffer-stop for railway stations and sidings was recently described in a paper read before the Institution of Mechanical Engineers by Mr A. Langley of Derby. This buffer-stop consists of two hydraulic cylinders fitted with pistons. The piston rods carry in front buffer-heads to meet those on the locomotive. There are also projecting rods behind the cylinders connected by chains with counterweights, to return the pistons after pressure to their former position. The pistons have a stroke of four feet; and it is calculated that this amount of depression would effectually stop a train without jerk or damage even if it were moving at the rate of eight miles an hour.
Gases inclosed in iron cylinders under enormous pressure are now used in various branches of science and art, and are supplied commercially by many firms in various countries. The gases most commonly used are hydrogen and oxygen—for the lime-light—carbon dioxide, and nitrous oxide—this last being much employed as an anæsthetic by dentists. Hitherto, there has been much difficulty in controlling the outrush of gas from these cylinders, for the internal pressure often amounts to six hundred pounds on the square inch. By the aid of a new regulator, invented by Messrs Oakley and Beard of London, this difficulty is at once obviated. The regulator consists of a small india-rubber bellows inclosed in a brass box, which screws upon the nozzle of the gas cylinder. By an ingenious device, as the bellows top rises with the pressure of the gas, a screw valve descends upon the opening in the cylinder. In this way the user of the gas can regulate the outflow to his requirements. We understand that it is in contemplation to adapt the same principle to ordinary gas consumption in houses, so that the supply may always be adjusted to the number of burners in actual use.
Habitual drinkers of aërated beverages were some time ago startled by the report that the original source of the water used in the manufacture did not much trouble the attention of the vendors, and that micro organisms in fabulous numbers might find their way to the consumers of these apparently innocent fluids. According to Dr T. Leone’s researches, aërated waters are peculiarly safe from such contamination. Taking a typically pure potable water, he tried how many micro organisms could be developed in it in a given time. In five days the water contained immense numbers of organisms. But when charged with carbonic dioxide, as all aërated waters must be to give them their effervescent quality, the number of living creatures was at once diminished. Water so charged contained at the end of fifteen days only a mere trifle of the original organisms. Dr Leone therefore concludes that the longer aërated waters are kept, the less chance is there of bacterial contamination.
The greatest living authority on bacteria, M. Pasteur, has by recent experiments proved that water containing only two per cent. of concentrated sulphuric acid possesses the property of destroying these organisms. He recommends that this acidulated water should be used as a disinfectant for floors of stables, mangers, courtyards, cattle-sheds, &c. The compound has certainly the merit of extreme cheapness, for about twelve gallons could be prepared at a cost of twopence. We may mention that M. Pasteur’s inoculations for hydrophobia have met with unlooked-for success. He recently told the Paris Academy of Sciences that out of three hundred and twenty-five cases of inoculation for this terrible disease, only one had proved a failure, and that one he attributed to delay. It is suggested that an international hospital should be established for the reception of patients from every country.
The all-seeing microscope has very often played an important part as an accusing witness, more especially in the identification of blood-stains. Recently in Illinois the same detective agent was instrumental in hanging a murderer; but the method of conviction was novel. Here is the case: A. had been found murdered while sleeping on a pile of sawdust in a certain icehouse, which we will call No. 1. B. was suspected of the crime because particles of sawdust were found on his clothing and on his boots. He accounted for this by pleading that he had been sleeping in another icehouse (No. 2) which was far away; and declared that he had not been near the No. 1 house. It was proved that icehouse No. 1 contained pine sawdust, and house No. 2 hardwood sawdust only. The microscope showed that the clothes and boots had attached to them particles of the former only. The man was convicted and executed.
Professor Vogel has lately brought forward the curious fact that the generation of alkaloids in plants is dependent upon sunlight. The hemlock plant which yields coniine in Southern Europe contains none in Scotland. Again, the tropical cinchonas, from which quinine is obtained, will yield very little of that valuable product if cultivated in our weakly lighted hothouses. Professor Vogel has examined many specimens of the plant from various conservatories, and has been quite unable to obtain the characteristic reaction of quinine, although the method of testing is a delicate one, and sensitive to minute quantities of the alkaloid. It is curious to observe that although sunlight seems so necessary to the formation of quinine in the living plant, it acts most injuriously upon the alkaloid in the stripped bark. In the latter case, the quinine is decomposed by it, and assumes the form of a dark-coloured resin. Because of this, in the manufacture of quinine, the bark is always dried in the dark.
The recent severe weather must have led many a half-frozen traveller to wonder if our railway and tramway Companies will ever hit upon some method of heating public conveyances. With a steam-engine as a necessary adjunct, it would seem to the disinterested inquirer that a method of warming by pipes fed from the ‘exhaust’ would be a comparatively easy way of managing the business, and would at the same time save much labour in doing away with the filling and distribution of inefficient foot-warmers. In Chicago, a new method of heating tramcars is being tried, and it promises well. The apparatus, which is placed under the floor of the car, consists of a brass cylinder filled with coal-oil, which, under pressure of a strong spring, is forced into a small super-heater, where it becomes vaporised. This oil-gas is ignited in a fire-clay combustion chamber, and although there is no flame, the fire-clay is brought to a white heat. The outer air passing over this hot box becomes well warmed, and a constant stream of fresh, warm air is assured to the passengers. The only visible evidence of the stove is a grating in the floor of the car through which the hot air rises. When will our tramway Companies consent to a small reduction in their high dividends, to afford their patrons similar comfort?
The use of wood pavements in Sydney has been very strongly condemned by a Committee appointed by the Legislative Assembly of New South Wales to inquire into the subject. It had been alleged that these wood pavements exerted a deleterious influence on the health of persons living in their proximity, and the conclusions arrived at by the Committee would seem to justify these allegations. Analysis showed that the blocks in actual use had absorbed a vast amount of organic matter, even though they had only been laid down a comparatively short time. It was evident, too, that complete impregnation of the wood was only a matter of time. In the words of the Report: ‘So far as the careful researches of your Board go, the porous, absorbent, and destructible nature of wood must, in their opinion, be declared to be irremediable by any process at present known; nor, were any such process discovered, would it be effectual unless it were supplemented by another which should prevent fraying of the fibre.’ It should be noted that this strong condemnation is applied to the hard wood-blocks used for the purpose of paving in Sydney, and not to the soft wood used here at home. These latter are so thoroughly impregnated with tar, that it is difficult to imagine that room could be found for anything else, organic or otherwise.
The cable tramway which is situated on the historic hill at Highgate, London, has worked without hindrance during the recent frost and snow. This is due to the fact that the working parts are underground. But of late a new use has been made of the system. Heavy vehicles even with six horses attached could not be moved up the hill during the recent frosts. Many of them were therefore fastened to the tramcars, and were pulled up the steep incline—one in eleven—at the rate of six miles an hour.