Page:Encyclopædia Britannica, Ninth Edition, v. 10.djvu/706

Rh ($84 description. Then follows Wyldis well known “great globe,” erected in Leicester Square, London, 60 feet in diameter. The largest appears to have been the one erected by Colonel Larrglois in Paris in 1825, on the Champs Elysées. This was 1:20 feet in diameter. As has been truly said, these structures served more to satisfy curiosity than to impart scientiﬁc instruction. (C. H. C.) .’|[anufucturc.-—-Tlre inanufacture of artificial globes has changed but little in character during the last hundred years. Such irri- provements as have been introduced have reference either to tl:e quality of the irraps or to the mode of mounting the globes. The number of sizes manufactured has also been increased. The diameter has always been used to indicate the size of the globes, aird those now produced by the various makers vary from 1 to 36 inches. The process of nraniifacture differs little if at all in the sizes of globes rarrgiirg between 3 and 25 inches. Thus supposing, for ex- ample, a 12-inch globe (the ordinary school globe) is reqirii'ed to be riradc, a spherical mould measuring sonre quarter of an inch less in diarueter is prepared on which to forrrr hemispherical caps that are to constitute a hollow fourrdatiorr for the globe. This mould, made preferably hollow for lightness, and having a central axle terrriiirat- ing in poles, is well greased on the surface to enable it to resist damp. To form the caps, strips of white paper, damped in ivater, are first applied to the mould to form a coating tlrercoir. Upon this coating is applied brown paper saturated with paste, and alternate layers of white and brown paper are added, until the required thickness of paper, say fctlr of an inch, is obtained. The cliairgc of colour is adopted simply as a guide to the workman, that he may know when he has coiirpletcd a coating of paper. The mould thus covered is put aside to dry, and after two or three days the paper covering is severed into two hemispherical caps, which are then drawn off from the mould. A wooden axle furrrislred with poles (which will eventually form the north and south poles of the globe) is provided, of such a length as will enable the caps, when fitted over the poles, to irieet at their severed edges. By means of glue these edges are joined up, and the ca s are firmly attached to the ends of the axle. Thus a hollow sp ere of rude oiitliire is formed, measuring somewhat less than 12 inches in diameter. The next operation is to bring this sphere to the required diameter for the globe, and to make it perfectly true. For this purpose the ball is coated with a plastic composition of whiting, boileil oil, and glue, and passed under the aetioir of a steel semicircle fitted with bearings for recciviirg the poles of the ball, and retaining the sarrre in place while the hall is being slowly rotated. By applying to the ball repeated coatings of this composition, and removing all siipcrflnitics by nreaiis of the gaiigiirg edge of this steel seirricircle, a smooth sphcrieal surface is eventually obtained. When the ball is finished and hard, it is tested in loose hearings to see whether it will remain quiescent in all positions. If it shows a tendency to run round, the ball is balanced by the introduction of a counterweight at the highest part of its eripliery. 'hen the ball is balanced, and the hole made good by w iiclr the counterweight was iirtrodueed, the surface is polished, after which it is ready to re- ceive the map. For 12-inch globes the maps of the earth and of the heavens are engraved on steel or copper plates in 12 gores, measur- ing each 30 degrees in width, and extending from pole to pole, or more usually to the 70th degree of latitude, the remaining portion of the riraps being made up by north aird south pole plates. This arrangement is somewhat iirodified for larger globes. Thus, for globes above 15 inches in diameter, the gores are divided in the line of the equator, and they are also divided longitudinally for say oire-fourth of their length at the 15th degree, in order to facilitate the laying down of the maps eveirl y upon the spherical surface. Prepara- tory to covering the sphere. with the map, it is nrar'kcd with lines corresponding to the equator, parallels of latitude, and lines of lon- gitude on the nrap, such lines serving as a guide for the workman.- 'l‘he gores of the map having been carefully cut out, they are damped and laid doivn in proper order in a pile upon a pasting board. The workman then covers his polished ball, for the leirgtlr and breadth of a gore, with paste, or, rirore properly, a preparation of starch, and having coated with starch the uppermost gore of the pile, he with an ivory knife lifts that gore, and lays it irpon the pasted portion of the ball, fitting it to tlrelirres marked thereon, and smoothing down creases, at the same time takin" care that the lati- tude and longitude lines of the vote eorrespoiid exactly with the lines_ on the ball. }lavi_ng laid down this gore in place, he next applies aseeond gore in like manner, taking care that the two gores shall join each other, and not expose any portion of the underlying surface. In this way the workrirair proceeds until all the gores are in place, and he ﬁnishes the pastiirg of the ball by applying the pole papers which fit respectively on to the opposite ends of the gores. The map has next to be sized, preparatory to its being coloured, in order to form a resist to the varnish which is siibsequcntly to be applied to the globe. The map is tinted and outlined wiili water colours, GLOBE and a coat of varnish is then applied. When this is dry the globe is ready for irioiiirtiiig; after which the varnishing opera- tion is corrrplcted by the application iii a heated roonr of several coats of spirit varnish following quickly the one on the other. Soirre skill is requisite in layiirg on the varnish, so as to obtaiir a surface as clear and srirootlr as glass. This result is iiirfortirnatcly evairesecirt, as the best varnish is liable to discolour and to crack, and thereby obscure to sorrre extent the lcgibility of the iiirdcr- lying map. After varnishing the globe will be lit to handle in froru foirr to six days. For the purpose of nroiintirrg the globe a flat riirg, terirrcd the brazen incridian, is provided, aird bearings are formed thereon to receive the poles of the globe. This ring is divided on its face into 360 degrees, the numbering of these degrees being from 0 (which correspoiids with the equator) to 91) at the poles on one half of the ring, aird on the other half the numbering starts from the poles at 0, running up to 90, which corresponds with the equator. Fitted to the poles, and capable of trrrrrirrg thereon, are hour circles, ivlriclr underlie the hr-a7.err meridian, and are divided and niirrrbcrcd to correspond with the 24 hours of the day and night. The frame for the reception of the globe and ring is formed with a wooden horizon, which consti- tutes an imaginary line dividing the globe into two equal parts, the portioir above the horizon being the visible half, aird that below the horizon the invisible half of the sphere. This horizon is covered, like the globe, with papers which are varnished to protect them from injury. The horizon papers near their inner edge are divided iirto 360 degrees, by which are reckoned the aziiirirtli and the airrplitiidc; they also indicate the points of the compass in the space called the circle of the winds. The horizon of the frarire is irotelred to receive the brass meridian, which rests in a step-bcarirrg fitted to the ccirtral pillar or block of the frame, and is held thcrcin by a screw stop, which, entering air arrniihir groove in the back of the iircridiair, leaves the ring free to turn round in the. frame, for the purpose of rectifyingthe globe, or bringing its axis to any desired angle with the horizon. The fitting of the globe is completed by the quadrarit of altitiule, consisting of a thin flexible slip of brass, jointed to a clamp- ing nut, which is iirtcirdcd to embrace the brass iricridiair, and rn.r_v be adjusted thereon by a tightening screw. This flexible strip or blade is divided off into 90 degrees, corresponding to those on the equator, and is intended to measure distances betwecir any two places upon the curved sirrface of the earth, or the altitude of the. snrr, a star, or any planetary body in the heavens, and for this pur- pose its graduations are rriiirrbercd from 0 to 90. A useful appendage to the globe frame is a mar-iner’s compass, which facilitates the adjiistnient of the globes to their true polar position. The value of a globe, whether terrestrial or celestial, dc iends mainly on the qirality of the rirap witlr‘which it is covered. lefore the pr'escirt century, Englislr globes were not only poor specimens of the e1rgraver's art, birt they showed little attention to II(‘( uracy of detail. Now, however, they rank in quality with, if they do not surpass, the best foreign maps, notwithstarrding that little encour- agerirerrt is given to their nizrirufaetiri'e. Specimens of globe plates published at the latter end of the 17th century in Italy are yet to be seen, which are a marvel of the eosmogr'rrplrer"s art. Uiider the patronage of the Venetian republic, 1’. Coronelli, eosrnographcr to the repirblic, published a tcrrcstri.il and celestial globe of the irri- preeedeirted size of 4 feet in diairretcr, which embodied the utmost scientiﬁc knowledge of the time, and in the constellations of the celestial globe showed the finest quality of line engravingat its lr(‘<f period. The eoirrposition of these figures served as a basis for the rcniodelling of the constclhrtioirs on F.nglish globes some -in years siirce, at which time the drawing of the figures was not llrt-ti'l_' barbarous, but absurd. 'hcther these fine globes were ever rrrairir- factiired it is now difficult to ascertain, but none are known to exist except a celestial globe prodiiccd by the late Mr 'illiarn Nci'torr, to wlroirr the globe maiiiifacture is iirdcbtcd for such ini- provcinents as have been iiitrodiiccd during the present century, and another which is preserved in the Bihliothcqiie Nationalc of Paris, bearing the rrairrc of l)eiivez as the rrrakcr. _ An ainirsing illustration of the (lllllLlllll(‘S which atteird the de- lineator of globe plates is to be found in the preface of a book published in 1686, for its author, Mr J. Moxon, eirtrtlcd A 7'utm' to A.s-lronomy and Geog:-aplry. Moxon appears to have been a glol)c-imrkcr, and in cxpatiatirig on the inrproveincnts to be found in his new terrestrial globe, he says:—“('alifor-nia is found to be an islaird, though formerly supposed to be part of the rrrairr continent, whose irorth-west shore was imagined to tlrrirst itself forth close to the coasts of Cathaio, and so make the supposed straits of Anian.” On his globe, therefore, the peirirrsiila was corrvertcd into an island. l'rt-eisely the same difficulties are now cx rericnccd by globe-makers; and those who have watched, for examp e, the varied forms which the lakes in Central Africa have takcir during the last 25 years will undcrstaird at what risk the globe-nrakcr corrects his costly plates, to bring them up to the eiirrcirt geographical knowledge. The inconvenience attendant on the transport of large globes, inairiifaetured as above explained, not to speak of their excessive cost, led to the iirtrodiietioir of flexible or compressible globes, both