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SCIENCE REVIEW, Is now ready, containing 550 pages of Letter-press and 27 Coloured and Plain Plates, price 12s. Cloth cases for binding the volume may be had, price ls. each.
No. I., price 23. 6d., contains :CORN. By Prof. James Buckman, F.L.S., &c. Illustrated by the Author.-The CROWN
ANIMALCULE. By Philip Henry Gosse, F.R.S. Illustrated by the Author.-Tax Daisy. By Mrs. Lankester. Illustrated.—The Lowest FORMS OF LIFE. By the Editor, with Illustrations.-IRON AND STEEL. By R. Hunt, F.R.S.-WESTERN EQUATORIAL AFRICA. By the Editor, with & Coloured Map.-ARTIFICIAL LIGHT. By Prof. Ansted, F.R.S.THE BREATH OF LIFE. By W. Crookes.-Dogs. By Ed. Jesse, F.L.S., &c.—THE GREAT COMET OP 1861, By J. Breen.
No. II., price 2s. 6d., contains :CAVERNS. By Prof. Ansted, F.R.S.-Lowest FORMS OF LIFE. By the Editor. Illustrated
by Tuffen West and G. H. Ford.—THE FLOWER ANIMALCULE. By P. H. Gosse, F.R.S. Illustrated by the Author.-COTTON. By Dr. Lankester, F.R.S. Illustrated by Tuffen West.-Grasses. By Prof. Buckman, F.L.S. Illustrated by J. E. Sowerby.-Toe REFLEX THEORY AND DR. MARSHALL HALL. By G. H. Lewes.-SOLAR CHEMISTRY. By R. Hunt, F.R.S. Illustrated with a Coloured Diagram.-OPTICAL PHENOMENA OP THE ATMOSPHERE. By G. F. Chambers.-Miscellanea, Reviews, and Scientific Summary,
No III., price 28. 6d., contains :THE PHOSPHORESCENCE OF THE SEA. With Plate. By A. De Quatrefages.—THE SUN AND
SOLAR PHENOMENA. With a Coloured Plate. By James Breen.-LIGHT AND COLOUR. With a Coloured Plate. By Robert Hunt, F.R.S. -The INTERNATIONAL EXHIBITION BUILDINGS. With Plate. By W. Fairbairn, C.E., D.C.L.-The ArPliCATION OF SCIENCE TO ELECTRO-PLATINO. By George Gore.-ARTIFICIAL Precious Srones. By W. S. Howgrave.-THE WHITE CLOVER. By Mrs. Lankester. With Two Plates by Tuffen West.-THE HUMAN HEART. By Isaac Ashe, B.A.-Miscellanea, Reviews, and a complete Quarterly Retrospect.
No. IV., price 2s. 6d., contains : Tax GREAT EXHIBITION OF 1862 : The Agricultural Implement Department, with Plate.
By Howard Reed.-The BRITANNIA AND CONWAY TUBULAR BRIDGES, with Plate. By W. C. Unwin, B. Sc.- PRIMITIVE ASTRONOMY, with Two Coloured Plates. By the Ed tor. -The Puysics Of A SUNBEAM, with a Coloured Plate. By R. Hunt, F.R.S.—TH8 ENOLISH CALIFORNIA. By G. P. Bevan, F.G.S.—THE CONTENTS OF CAVERNS (con. cluding Part). By D. T. Ansted, F.R.S.-Tue MICROSCOPE, with Directions for its Use. By C. Collingwood, M.B., F.L S.-The BuildER ANIMALCULES, with Plate. By P. H. Gosse, F.R.S.-The COMMON TRUFFLE, with Plate. By Jabez Hogg, M.R.C.S., &c.Miscellanea, Reviews, and Scientific Summary of Progress in Science.
No. V., price 28. 6d., published October, 1862,
Contains, with other interesting mattor :THE BRITISH OAK, with Two Page Illustrations. By Prof. James Buckman, F.L.S., F.G.S.,
&c.-Tubifex RIVULORUM, the Red Worm of our Rivers, with a Coloured Plate. By Edwin Ray Lankester.-ANÆSTHETICS. By Dr. T. L. Phipson, M.B., F.C.S., &c.—BARMOUTH, and its Scientific Attractions, with a Tinted Ilustration. By the Editor.-Tur ELECTRO-PLATING PROCESS (concluding Part), with an Illustration. By George Gore.NOTES OF THE EXHIBITION: II. The Mineralogical Department. By Prof. D. T. Ansted, F.R.S. III. The Chemical Department. By W. Crookes, F.C.S., Editor of the Chemical Neus. IV. The Philosophical Instruments. By James Breen, F.R.A.S.-Miscellanea, Reviews, and a coniplete Summary of Scientific Progress.
No. VII.-April, 1863, Will contain, amongst its original contributions :THE AFRICAN LION IN ITS Native Haunts (being a brief sketch of its Natural History). By M. Jules Gerard (the Lion-killer).
(Translated by the Editor). OUR FRESH WATER PolyzoA. By the Rev. W. Houghton, M.A., F.I.S.
And other papers of interest.
NOTES OF THE EXHIBITION.
BY WILLIAM FAIRPAIRN, LL.D., F.R.S.
section of the Great Exhibition afforded so deep an
interest to all classes of the British public as the Machinery Department.
Whilst in other divisions it was the object of our neighbours to excel us, all they could hope to do in the province of mechanical engineering was to stand on the same level, and compete with us in a friendly rivalry of skill in constructive art. In many instances they succeeded; but we believe that every connoisseur of the subject who visited the Exhibition, and every reader of the following remarks, will agree with us in thinking that, notwithstanding the rapid and creditable progress made elsewhere, Great Britain still holds the proud position of being at the head of nations in mechanical appliances and engineering proficiency.
A word of apology before we commence our task. Amongst the numerous readers of this Journal, many are well acquainted with the technicalities of natural science,-less, probably, with those of the engineering arts; and if here and there we have been led to employ terms of a technical character, it must be remembered that we are dealing with embodiments of the conceptions of the most advanced minds of the day, and we are compelled to refer to the application of principles which few can fully understand.
As far as possible, however, we have endeavoured to steer clear of abstruse subjects; and if we should occasionally touch upon principles, or their applications, which some of our readers do not fully comprehend, we hope that they will be tempted to inquire further and make themselves masters of their precise character.
In order to enable our readers to form a clear conception of
the advanced stage to which the mechanical operations of the engincer have attained, it will be necessary to examine 1st. The sources from which we obtain the elements of
motive power, comprising the steam-engine, its
varieties, forms, and application. 2nd. Water-power, as exhibited in water-wheels, turbines,
and other hydraulic machines. 3rd. Grinding, crushing, and cutting machines. 4th. The machinery for the manufacture of textile fabrics. 5th. Locomotive machinery and railway plant. Lastly. The machinery of agriculture. In following these divisions of our subject, we have for the source of all power the heat of the sun, which, according to the last new theory of Professor W. Thomson and Mr. Waterton, is produced and maintained by a constant shower of meteoric matter which falls into that luminary. Assuming this to be true, a continuous supply of cosmical heat will produce any description of motive power, which we convert into mechanical force by the combustion of fuel, and by this and other contrivances abate the necessity for muscular exertion in man and animals. To the same source may be traced the vivifying principle of animal and vegetable life; and the deposits of past ages, which we are now using as an agent of accumulated force or work accomplished, and which constitute, in almost every case, the necessary conditions where motive power is required. To the labours and experiments of Black, Carnot, Mayer, Regnanlt, and Joule we are indebted for the two principal laws of thermo-dynamics, which are, according to the construction of Mr. Mallet, thus stated, namely :
That heat and mechanical force are reciprocally convertible, and heat on being evolved, requires, or when it disappears, returns in mechanical forec, an equivalent of 772 foot-pounds for cach English thermal unit, viz., for the heat of one degree of Fahrenheit's thermometer in one pound of water.
In other words, an increment of heat that will raise the temperature of one pound of water one degree is equal to raising 772 lb. one foot in height. This is Joule's equivalent, and has now become general as a measure of work done in footpounds.*
Steam and steam-engines are the most important agents now in use as a motive power in Great Britain, and from these alone we receive nearly the whole of the force that is at present
* The resistance of one pound evercome through a distance of one foot is called a foot-pound.
in operation in manufactures, steam navigation, locomotion, and mining. The extent of this force, in this country alone, has been differently estimated. In 1859 it was nearly as follows:
Or about 11,000,000 horses' power, raising 33,000 lb. one foot high in one minute, or equivalent to the enormous force of raising 162,053,575 tons one foot high in one minute, or 1,620,535 tons to the height of 100 feet in the same time. This was estimated as the work done per minute three years ago; now it has increased to upwards of 12,000,000 horseswhich may
be taken as the motive force in the British isles alone.
It would be interesting to know the quantity of coal consumed for the purpose of generating a force equivalent to raising the above enormous load of 9,723,214,500 tons one foot high in an hour. This, as already stated, would require the strength of 11,000,000 horses to accomplish in one hour, and this multiplied by five, the average consumption of coal per hour per horse-power, gives 24,533 tons, or about 25,000 tons, as the rate of consumption per hour for the steam-power of Great Britain and Ireland.*
Steam-Engines are of three classes, -Stationary, Marine, and Locomotive; and these are again subdivided into Condensing and Non-condensing Engines. Nearly all at the present time work the steam expansively; that is to say, they are so arranged in the construction of the valve motions, as to cut off the communication with the boiler at one-third, one-half, or two-thirds of the stroke, as the case may be, in regard to pressure, or the power to overcome the resistance of the load. Some engineers go so far as to cut off the steam at one-sixth and one-eighth, and expand the remaining five-sixths or seveneighths of the stroke.† The expansive system is now thoroughly
* Vide " Useful Information for Engineers," p. 206.
† The distance which the piston travels is called the stroke, and is twice the radius of the crank.
understood, and is in almost every case resorted to, with a great saving of fuel. Of late years the principle of expansive working was very imperfectly understood, and the result of its introduction was an immense economy; for more than double the quantity of work is now done with the same quantity of fuel, of what was formerly accomplished on the old non-expansive principle. It must, however, be borne in mind, that this cannot be effected without an increase of the pressure of steam, and hence follows the necessity of having the boilers of increased strength and improved construction. The neglect of these precautions has resulted in serious and fatal accidents, attended with a considerable loss of life and property.
Irrespective of increased pressure, and working the steam expansively, the speed of the engine has been increased about one-third since the days of Watt. In his time the piston of the stationary engine travelled at the rate of 240 feet per minute; now it averages from 300 to 320 feet, and this, combined with high-pressure steam worked expansively, increases the power of the engine, in some cases, upwards of twofold, and, as already stated, doubles the quantity of work done with the same quantity of fuel. Thus an important saving is effected to this and every other country where steam is employed as an agent of power and motive force.
Having ushered in our observations with these necessarily technical remarks, we may state that the Exhibition of this year does not present any new nor original conception in the construction of stationary engines, with the exception of the non-condensing engines, which, in this case, have their cylinders horizontal instead of vertical, as exhibited in the old construction. There are some advantages in this, as the cylinders of the non-condensing engines are comparatively small, and are less liable to wear oval than would be the case in the large condensing engines. These engines are, however, chiefly used as assistants to the stationary condensing engine, and effect a saving by the steam being employed twice over, for it first propels the piston of the high-pressure horizontal engine, after which it is conveyed to the cylinder of the large condensing engine, where it finishes the work at a considerably reduced pressure.
These double engines are mere substitutes for the compound engine of Woolf,* with this disadvantage, that considerable loss is sustained by condensation in the transfer from one engine to the other; and taking into account the back pressure and other causes, this combination is less effective than the united compound engine. But exclusive of
* Woolf is the inventor of the double-cylinder engine.