« السابقةمتابعة »
From back tube-plate to back of fire-box. From crown of furnace to top of fire-box. Number of air-holes in furaaco fronts and
door. Diameter of each. Is there a slide on these? From top of fire-box to crown of boiler. From top of fire-box to top of steam-chest. Size of steam-chest.
Steam room in each boiler in cubic feet. With water-level, inches above fire-box crown.
Are the boilers dry-bottomed?
Number of tubes for each furnace, in height.
Ditto in width.
Ditto, left out for stays.
Length of tubes.
Inside diameter of tubes.
Chimney—diameter at uptake.
What is the difference between the inches in the vacuum-gauge and the inches on the ship's barometer taken at the same time?
Pressure of steam in boilers.
When at full speed, what is the difference between the steam-gauges at the boilers and near the cylinders?
Is there a good command of steam?
Is there flame in the smoke-box?
Revolutions of engines per minute.
Please enclose indicator diagrams, and mark each one thus, or in some other intelligible way:—
which reads thus:—Aft engine top of piston; Grade of expansion J; Steamgauge 14; Vacuum-gauge 23; Revolutions of engine 45; Speed of vessel, in knots, per hour 12; Mean draught 13 ft. j Rushby Park Coals, per hour, 7i cwts.
If the speed of vessel be given in statute miles, write M instead of K.
Instead of AT write AB, FT, FB, as the caso may be. If convenient, after V insert which reads, Barometer 29 in.
You are also requested to fill up as many lines of the following Tables as you have an opportunity of doing.
Table Op Peepobmance Todee Tbiat, Undeb Steam Aioite^ndeb Sailaloite, Amd Undeb Steam And Sail Combined.
Number of Trial.
Direction of wind.
Force of wind.
State of sea.
Duration of trials.
Area of sail set.
Description of sail set.
Average speed per hour.
Consumption of coal per hour.
Quality of coal.
Diagrams enclosed, No.
Draught of water.
Pitch of screw.
Grade of expansion.
Revolutions per minute.
Number of furnaces at work.
Note.—Trials Nos. are under steam
only, and Nos. under steam and sail
On the Fall of Rain in the British Isles during the Years 1860 and 1861. By G. J. Symons, M.B.M.S.
Before entering on the consideration of the rainfall during the last two years, it 'will be well to offer a very few preliminary remarks on the various causes which affect the amount of rain collected, and also briefly to state in what manner the information given in the following Tables has been verified.
The first requirement is obviously that the gauge should be rigorously accurate, and placed in a suitable position; but it is equally obvious that the satisfactory fulfilment of these conditions can only be determined when every
gauge has been visited and tested by some person well acquainted with, the subject, and provided with the necessary apparatus. This examination, involving as it does the testing of more than 500 instruments, scattered far and wide over the British laics, from Galway on tho west to Norwich on the east, from the Shetland Isles to Guernsey, cannot be completed for several years, and is, moreover, not indispensable; for adjacent stations will generally enable us to determine if any large error attaches to either the instrument or its position. For the present, then, it is a matter, not of choice, but necessity to take the readings as recorded by the observers; and as the majority of the gauges already tested have borne the examination satisfactorily, it is presumed that this may be safely done.
In the next place, it is almost needless to say, that unless the height of the rain-gauge above the ground and above sea-level be known, the records are not comparable with other stations; for every foot of elevation above the ground is believed materially to diminish the amount collected, and every increase in the height above the sea-level to increase it. These particulars are therefore given wherever they are known; but the values must be received, subject to revision when the stations have been visited and the elevations accurately determined.
It is, of course, almost impossible to secure perfect accuracy in such an extended series of returns as are combined in the following Tables, but I believe they are very nearly perfect. The information was sent to me by the observers in reply to circulars issued at the close of each year; the returns, as received from them, were classified into counties and districts, examined, all errors being sent back for explanation, and copied into the following Tables, which have finally been checked against the observers' MS. returns.
The excessive rainfall in the Lake District of England having caused considerable interest, not to say incredulity, it may be well to add a few words in entire confirmation of the perfoct veracity of the returns.
The gauges were mostly erected in 1844 or 1845, by Dr. Miller of Whitehaven, whose known accuracy might alone be a sufficient guarantee; but, besides this, there is the personal experience of those who, like myself, have studied the rainfall of that district, as alone it can be properly studied, dwelling amid the mountains and watching the effect of each summit on the drifting clouds, whether driven by a heavy gale or merely floating on a gentle breeze.
To make certain that the gauges were as accurate as when originally erected, I recently lent my friend Mr. G. H. Simmonds the necessary apparatus; he has carefully tested several of the gauges, and, so far as the calculations are concluded, we find them strictly accurate.
The stations have been arranged on the plan employed in the Keports of the Registrars-General of England and Scotland, except that the ordinary county boundaries aro maintained, and that the stations in each county are arranged in the order of latitude from south to north. In Ireland, the arrangement is merely according to latitude.
The counties comprised in each district are enumerated in the following List, so that tho fall at any station may be referred to in the general Tables with the greatest facility.
England And Wales.
Division I. Middlesex.—Middlesex.
„ II. South-eastern Counties.—Surrey, Kent, Sussex, Hants, Berks.
Division V. South-western Counties.—Wilts, Dorset, Devon, Cornwall, Somerset.
„ VI. West Midland Counties.—Gloucester, Hereford, Shrop
shire, Stafford, Worcester, Warwick.
„ VII. North Midland Counties.—Leicester, Eutland, Lincoln,
„ VIII. North-western Counties.—Cheshire, Lancashire.
„ X. Northern Counties.—Durham, Northumberland, Cum
„ XI. Monmouthshire, Wales, and the Isles.—Monmouth, Gla
morgan, Pembroke, Cardigan, Anglesey, Carnarvon, Flint, Guernsey, Scilly, Man.
Division XII. Southern Counties.—Wigtown, Kirkcudbright, Dumfries. „ XIII. South-eastern Counties.—Selkirk, Peebles, Berwick,
Haddington, Edinburgh. „ XIV. South-western Counties.—Lanark, Ayr, Renfrew. „ XV. West Midland Counties.—Stirling, Bute, Argyll. „ XVI. East Midland Counties.—Kinross, Fife, Perth, Forfar. „ XVII. North-eastern Counties.—Kincardine, Aberdeen, Elgin. „ XVIII. North-western Counties.—Boss, Inverness. „ XIX. Northern Counties.—Sutherland, Orkney, Shetland.
Division XX. Lreland.—All the Counties whence returns have been received.
The fall at a few of the stations has been laid down on the accompanying Map, with the double object of illustrating the relative fall in different parte of the British Isles, and the relation, in each locality, between the fall in 1860 and 1861. This has been done in the following manner:—Darkly shaded discs uniformly represent the fall in 1861; lightly shaded, that in 1860. The radii of the circles are half the scale given on the Map; the diameters therefore increase as the fall; and hence the increased diameter of the circles immediately points out the places of heaviest fall. The relative frequency and extent to which either the darkly or lightly shaded circles extend beyond the others shows which year had the heavier fall; and the breadth of the annulus shows by how much it exceeded the other.
In selecting the stations for insertion in the Map, preference was given to those less than 200 feet above mean sea-level, and at which the gauge was within a few feet of the surface of the ground. It was not found consistent with good geographical distribution to adhere rigidly to these requirements in every case, but the exact height may be readily ascertained by reference to the general Tables. The fact, however, that the mean height of the selected gauges above the ground is, in England, 1 ft. 4 in.; in Scotland, 1 ft. 11 in.; and in Ireland (omitting Cork), 7 ft. 7 in.; and above the sea, 131,177, and 108 ft. respectively, shows that a near approach has been made to the fulfilment of these conditions. The paucity of stations in Ireland necessitated the use of rather elevated gauges; in the case of Cork, the Map shows the fall at the ground oomputed from the fall observed 50 ft. above it, as otherwise it would not have been comparable.
It is remarkable, and perhaps suggestive, that in 1860 the excess in South Britain was counterbalanced by a deficiency in Scotland; and that in 1861 the equipoiso was maintained, but in the reverse order, England being comparatively dry, and Scotland (especially the western coast) subject to almost unprecedented rains. It is also most noteworthy that, if the returns from all the stations in England, Scotland, and Ireland are combined, the fall is nearly identical in the two years. In 1860, the average fall at 390 stations was 39-784 inches; and in 1861, 38-466 inches.
The singularity of this result is fully shown by Table I., which gives the average fall in each district for each year, and the excess or defect in each district of 1861 over 1860.
Table I.—Average fall of Bain in 1860 and 1861, and difference between
the two years.
The next point for consideration is the relation which subsists between the fall in the two years, 1860 and 1861, and the average of a long series of years. A largo number of the gauges having only been in use for ten or
Table II.—Difference between mean Rainfall, as obtained from long series of years, and from the ten years, 1850 to 1859.