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INSTRUMENTS

FOR TAKING OBSERVATIONS AND DRAWING UP A MAP.

It will add greatly to the interest which a traveller may take in drawing up a large and graphic route map of his journey, to be assured of the extreme ease and cheapness with which copies of such a map may be multiplied to any extent by a well-known process in lithography; since these being available for distribution among persons interested in the matter, will prevent his painstaking from being lost to the world.

The method I refer to is that of autographic ink and paper; it can be obtained with full instructions at any lithographer's shop. The paper is prepared by being glazed over with a composition, and the ink is in appearance something like Indian ink, and used in much the same way. With a pen and this ink, and upon this paper, the traveller draws his map; they are neither more nor less difficult to employ than common stationery, and he may avail himself of tracingpaper without danger. He has one single precaution to guard against, which is not to touch the paper overmuch with his bare hand, but to keep a bit of loose paper between it and the map as he draws.

As soon as finished, the map is taken to the lithographer, who puts it face downwards on a stone, and passes it under his press, when every particle of ink leaves the surface of the paper, and attaches itself to the surface of the stone precisely as though it had originally been written there: the glaze on the

paper, which prevents the ink from soaking into it, makes this transference more easy and complete.

The stone can now be worked with, just as a stone that has been regularly lithographed; that is to say, printing-ink may be rubbed over it, and impressions taken off to any amount. It will be observed that the writing on the paper comes off reversed upon the stone, and is re-reversed, or set right again, in the impressions that are taken from it.

The lithographer's charges for furnishing autographic ink and paper, working the stone, striking off fifty copies of a folio size, and supplying the paper (common white paper) for the copies-in fact, every expense included-need not exceed ten shillings, and may be much less.

If, before drawing out his map, the traveller were to go to some working lithographer, and witness the process, and make two or three experiments on a small scale, he would naturally succeed all the better. A map drawn on a large scale, though without any pretension to artistic skill, with abundance of profile views of prominent landmarks, and copious information upon the routes that were explored, written along their sides, would be of the utmost value to future travellers, and to geographers at home.

I reprint here part of a short paper that I have communicated to the Royal Geographical Society, and which will be found at the end of their volume for 1854. In addition to it, communications are also published there from Lieutenant Raper, Captain Fitzroy, Admiral Smith, Captain Beechey, and Colonel Sykes; the whole being collected under the title of "Hints to Travellers."

My own object was to suggest a complete and efficient outfit of simple instruments to explorers; to which end I gave the following list:

A SEXTANT—

LIST OF INSTRUMENTS.

A sextant of five-inch radius, light in weight, by a first-rate maker, divided clearly, and on platinum, to quarter degrees. It must have a ground-glass screen fixed in front of the reading-off lens, to tone down a glaring light, and a coloured glass to screw on to the telescope for index error purposes, in addition to the coloured shades. The handle must be adapted for fixing on the telescope stand. (It is recommended by Captain Beechey that the traveller's sextant should be on a plan which will measure accurately any angle, and that its telescope should have a horizontal line in its focus, and be fitted with a spirit-level, after the manner of levelling instruments; for when so fitted and screwed to a stand, altitudes of hills, and of stars when low, may be observed with it.)

A SEXTANT

A sextant of three-inch radius, graduated boldly to half degrees, in a leather case, like that of an azimuth compass, suitable for slipping on to a leather belt and being worn round the waist, if required.— Reserve, a second five-inch sextant, or other angular instrument of whatever kind the traveller may wish to take.

ARTIFICIAL HORIZON

The trough must not be less than 3 inches, inside length; it must be of the usual construction for filtering the mercury when it is poured in. The glass screen must be a folding one, and by a first-rate maker. Reserve, one spare glass and a strong two-ounce glass bottle full of mercury, wrapped up loosely in a roll of clothes, and well tied up and labelled.

(The trough should rest on a metal plate, the size of a thin octavo

book, with three knobs of an inch long for legs; this gives a steady rest when the ground is uneven, and raises it above the grass, &c. Dark or inky water will do nearly as well as mercury.-Report of SubCommittee.)

WATCH

A common, strong, silver watch, not too heavy, with an open face and a second-hand; it must wind up at the back. The hands should be black steel, not gilt, and they and all the divisions should be very clear and distinct. The performance of the watch is really a very secondary matter. 47. is quite enough to give for it.-Reserve, at

least two other watches of the same character; these should be rolled up separately, each in a loosely-wrapped parcel of dry clothes, say of old stockings, and they will never come to harm: they should be labelled, and rarely opened. Half a dozen spare watch glasses, fitting easily; two to each watch. Three spare watch-keys; one might be tied to the sextant-case, one wrapped up with each watch.

COMPASS

An azimuth compass, graduated from 0° to 360°; and if the maker understands how to do it, have a shield of brass cut out here and there, to admit light, fixed over the glass.-Reserve, two spare glasses and a second azimuth compass.

Three common pocket compasses, from an inch to an inch and a half in diameter. Their needles must carry cards graduated, like those of the azimuth compass, from 0° to 360°, in addition to the points. These compasses should be very light in weight, have plenty of depth, and be furnished with catches. The needles should work steadily and quickly. Avoid one that makes long, slow oscillations.

TELESCOPE

One of 23-inch object-glass, for observing occultations of small stars, and eclipses of Jupiter's satellites. The buyer should test it on the satellites, and be himself satisfied of its power before concluding the bargain.

STANDS

A clamp, to screw into a tree or a block of wood for the purpose of holding the telescope or sextant; one with three legs is perfectly useless to a traveller, for he has no table or anything else to put it on.

The ordinary telescope clamp makes a very good rest for a sextant, by clamping a rod of wood, one end of which is weighted as a counterpoise, and the other, ending in a neck, is pushed through an augerhole in the sextant handle, with a linch-pin stuck through its projecting end. Smooth action is not at all wanted for a sextant-rest.

THERMOMETERS

Two boiling-point thermometers. (Try them yourself against a good barometer to learn their index errors, at least; and recollect that for

all purposes of determining heights, common water does just as well as distilled water.)

Two or three common thermometers, graduated to 160° at least, if for hot climates.

A pot arranged to boil the thermometer in.

LANTERN

I can only suggest a "bull's-eye," which was what I used: I wish I knew of a better. A small ball of spare wick. Abundance of lampoil.

MAPPING INSTRUMENTS

Protractors-1 large circular brass one, 4 or 5 inches in diameter; 2 semicircular brass ones of 3 inches; all graduated, like your compasses, from 0° to 360°, and not twice over to 180°.

A station pointer for protracting sextant angles.

Two or three rulers, of 1 foot each, in ivory; a small square; a set of scales; small parallel rulers; compasses with pencil and pen; small pair of reserve compasses; fine ruling pen; a dozen artists' pins. Medium-size measuring-tape, say 12 yards; pocket ditto, 2 yards.

ADDITIONAL INSTRUMENTS, NOT NECESSARY, BUT CONVENIENT— A pedometer of the best construction.

An Adie's sympiesometer.

I cannot recommend an explorer to have anything to do with either a chronometer or a mountain barometer.

STATIONERY

A light board of the very best mahogany, to rule and draw upon, as large as the writing-case will hold, say 11 inches by 7.

Plenty of metallic note-books, with spare pencils, all of one size, say

5 inches by 3, or larger, with a leather pouch, having a flap buttoning easily over, and sewn on to the belt, to hold the one in use. Two (or three) ledgers of strong ruled paper, 11 inches by 7, each with a leather binding; the pages should be numbered, and journal observations, agreements, sketches, and every single thing that is written, written in them.

Plenty of spare paper; it should be smooth, sufficiently thick, and fold up into 11 inches by 7.

A sheet of blotting paper cut up and put here and there in the ledgers.

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