444
Class 10.—PHILOSOPHICAL, MUSICAL, HOEOLOGICAL,North, North Central, and South Central Galleries.
[Unite p
l-100th of an inch to 6 feet in diameter; elliptical in-struments, complete set of scales, standard measure andtriangles, also complete set of water-colours.
Improved dumpy-level, being simple in its adjustments,and strengthened by having the bar which supports thetelescope placed vertically instead of horizontally. Thesame with compass. 5-inch and 6-inch transit theodolites.30-inch transit instrument.
New instrument for measuring the distance of accessibleand inaccessible objects.
Opisometers, or map-meters, for measuring curvedlines.
Wheel and pediment barometers, carved to illustratethe four seasons. Gothic barometer. Ebony and goldbarometers.
Astronomical telescope. Naval and military telescopes.
Opera-glasses, with variously-coloured bodies.
Scale, with slide, for comparing the following mea-sures :—Swedish, Turkish, Bavarian, Spanish, Portuguese ,Moscow, Russian, Amsterdam, Rhynland, French , andEnglish .
Improved slide-rule, adapted for the use of the prac-tical engineer, having all the necessary tables for calcu-lating metal, earth, and wood works, with useful foreignmeasures.
Thermometers. 15-inch azimuth and altitude instru-ment.
322 Lloyd, Lieut-Col. J. A., F.R.S.—Inventor.
Typhodeictor, (from or tufose , and or
deletes ) or storm-pointer, an instrument for obtaining,by inspection, the bearing and relative position of arevolving storm or hurricane. Manufactured by Elliott& Sons.
It is now a well-ascertained fact that great storms havea rotary motion like whirlwinds. The theory, commonly
called the “ law of storms,” as made known m
se?® 1 *
•jil
rms, as maae kho'vu w* ■;
publications by Colonel Reid, has been established tthousands of well-authenticated observations in dine ^parts of the world, and extending over several y earS * ^proves that during a gale of wind, particularly D ® a jthe tropics, the winds blow with the greatest fury^® ^a common centre. At this centre, there is little** 5 awind, even a perfect calm, but there is, geue rai j’terrific and confused sea. .
The most violent and dangerous part of these l ] e ^ 0 Ji, e i?gales, is somewhere near this central calm, the wind t ^blowing the most fiercely, acquiring, it is stated, a «city of even 100 miles per hour. These storms s \ ^both land and sea, in certain parts of the globe; 1 jtrack and direction are pretty well known; and they ^bodily from their place of origin to their destinati° ^variable speeds; sometimes at not more than the *' a 0 f4 to 6 miles an hour; sometimes, but seldom, a .
20 to 30 miles an hour, although the wind withinrange is blowing round with the fury above mention® ■
If a ship, unhappily, becomes entangled within the i aof these terrible gales, she is in great peril; many » ^foundered, and others have pursued their fearful co ,round and round, until they have been reduced toless wrecks, dismasted and water-logged. ull d
In the northern hemisphere, these winds blow r ythe compass from east-by-north to west, or the conway to the hands of a watch; whereas, in a southemisphere, it is just the reverse, blowing round aS ^hands of a watch would go. This principle mas ^always borne in mind, as the very foundation of alinformation to be sought hereafter. . eei i
On these most valuable data, instructions havedrawn up by Colonel Reid and others, how to asC j t }sthe relative position of a gale, so as to know whetherapproaching to, or going from a ship, travelling by i ts s * tsor passing across its path. The following cut repi’ eSthe Typhodeictor.
Colonel Lloyd’
The object of the instrument is, by graphic illustration,to show that, when the wind blows from a particularpoint of the compass, you can only be in one relativeposition in regard to the centre of the whirlstorm, so that,either the storm is approaching the ship, or the shipapproaching the storm, and first of course encounteringthe outer edge.
As a consequence of the law of rotation, the wind, sup-posing the whirl to be circular, must blow at a tangent, orat right angles to the point of the compass, where the shipor observer may be, but under diametrically oppositeconditions, as far as regards the two hemispheres.
Thus, in a northern hemisphere, if the wind blowseast, the centre of the storm must be due south of theobserver; blowing north, the vortex east; coming fromthe west, the centre of the gale is due north; and, lastly,
’s Typhodeictor.
with the wind south, the gale is due west. Of c0 . tlI * s ’sd ethe intermediate points of the compass, the bearmolikewise different. r0l i«d
In a southern latitude, the whirlstorm blows s toi ,Jl1just the contrary way. With an east wind & ^estcentre bears north ; with a north wind, west; W«nwind, south; with a south wind, east. _ it > s
Bearing in mind these facts, and with sea roo ^ gll b-easy not only to avoid a hurricane, but to maKservient in many cases to the ship’s ultimate cou
Instructions. . rea sinl?’
When the barometer is falling and the wind in® rg( j (setset the large pointer of the instrument marked 1 froi’ 1this to the wind), to the true point of the compwhence the wind blows, corrected for variation.