the period, they make transition to them. light to the third period in 1864; W. H. observers to the fourth in 1892.

Dawes thus made twiPickering and the Lick

7. Distinct phenomena characterize the three periods. Patches of light and shade make the markings shown on the maps of the first stage of cartography. Of a piece though these patches are, their shapes appear well defined. At first one might suppose such to be due to the handicraft of the draughtsman and to possess no scientific value. But inspection of the several charts, one after the other, shows that the shapes are not artistic embodiments of ill-seen shadings, but are intrinsic traits of the shadings themselves, for chart after chart reproduces the same turns and twistings.

8. To see this we have but to take up in sequence the maps from 1840 to 1876. No. 1 of the series shows a cordon of patches

FIG. I.

20 30 40

NO DO

170 180 190 200 210 220 230 240 250 260 20 280 290 300 310 320 330 340

• 20 30 40 50 60 70 80 90 100 110 120 130 100 150 160 170 180 190 200 210 220 230 240 3:50 260 270 280 290 300 310 620 330 340 350 360 330 380 390 PROJECTED FROM BEER & MÄDLERS CHART

MARS 1840

Map of Beer and Mädler, 1840.

stretching round the map at about 30° south latitude. Their height is greatest at 90° of longitude, and from this slopes down through 360° to 20° longitude, whence it gradually rises to the maximum. At the point of maximum is an oval marked out by broad shading on the south, by narrow penciling on the north, and holding a roundish dark spot in its centre. This is the Solis Lacus, the eye of Mars. To the right of it follows a leech-like patch, the Mare Sirenum and the Mare Cimmerium seen as one. After this comes

a large dark area in the shape of a funnel, the Syrtis Major. Then a ribbon ending in a scroll, the Sabaeus Sinus, the adopted zero point of Martian longitudes.

9. In map No. 2, Kaiser's, all these features can be followed, from the eye with its eyebrow and the curve of its lower lid down through the chain of seas back to the oculus again. The various other dark markings on the map can be similarly identified.

4371

10. A very different set of phenomena stamps the advance made in the second period. Over the bright portions of the map is now drawn a network of fine lines. The dark patches remain as before. These singular lines are what are known as the "canals" of Mars.

II. The second period was the work of Schiaparelli. Of it are here given four maps, all that he made on Mercator's projection.

Oriens

After the opposition of 1883-84 he drew only maps with the pole
for centre, because of the tilt of the Martian axis which exposed
the northern regions and hid the southern ones.

The distinctive features of these maps are the "canals.”

The

"canals are objects as technical in character as they are in name, being quite unlike any other planetary detail. They are narrow lines of uniform width, of uniform direction and following usually

FIG. 8.

MERIDIES

200 270 280 290 300 310 330 300 340 350 0 10 20 30 40 50 60 70 80 90 100 No 120 130 140 150 160 6 180 190 200 210

) 200 250 260 270 280 230 300 310 320 300 340 550 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 30

the arcs of great circles. Tenuity, regularity and intercommunication are the traits which make them sui generis. Such precision

OCCIDENS