6r8 



SCIENTIFIC NEWS. 



[Dec. 21, 1888. 



range of rigidity according to whether it is slowly or 

 rapidly cooled. Ordinary tool steel, when annealed, maybe 

 beaten, or rolled, or " spun " into almost any shape. I 

 have before me a steel vase, 4 inches high, and 2 inches 

 in diameter at its widest part, shaped with foot, etc., 

 that was hammered and spun into its present shape 

 from a flat circular disc of rolled metal. On the other 

 hand, if tool steel be made red-hot and suddenly cooled 

 it becomes so hard and rigid that it will cut glass, and 

 may not be bent at all without fracture. This same 

 piece may be tempered through all the well-known 

 gradations down to the softness and plasticity above de- 

 scribed. It may be that Sir W. Thomson carefully 

 considered these facts in order to be quite safe in stating, 

 as the result of his calculations, that the rigidity of the 

 earth nearly corresponds to that of steel. 



That the earth, regarded as a whole, is elastic 

 and fluid, or viscous, in the sense I have described above, 

 is proved by the simple fact that great and small waves 

 are propagated in the course of earthquakes, and that 

 when the pillars of coal-mines are removed the roof 

 of rock sinks down and the floor " creeps," up, this occur- 

 ring in many cases without any fracture. 



Describing the Jamaica earthquake of 1692, Lyell says, 

 " A tract of land round the town, about a thousand acres 

 in extent, sank down in less than one minute, during the 

 first shock, and the sea immediately rolled in. The 

 Swan frigate, which was repairing in the wharf, was 

 driven over the tops of many buildings, and then thrown 

 upon one of the roofs, which it broke." He also tells us 

 that " the surface of the country during the Calabrian 

 earthquakes often heaved like the billows of a swelling 

 sea, which produced a swimming in the head like sea- 

 sickness. It is particularly stated, in almost all the 

 accounts, that just before each shock the clouds appeared 

 motionless ; and although no explanation is afforded of 

 this phenomenon, it is obviously the same as that ob- 

 served in a ship at sea when it pitches violently. The 

 clouds seem arrested in their career as often as 

 the vessel rises in a direction contrary to their course ; 

 so that the Calabrians must have experienced precisely 

 the same motion on land." 



In the report of the Committee appointed by the 

 British Association (1885) to investigate earthquake 

 phenomena in Japan, some very curious facts are stated. 

 One of the instruments used for measuring the move- 

 ments of the earth was carried to the summit of Fuji- 

 yama, a mountain 12,365 feet high, and it was found 

 that the effects of the earth-waves' movements were 

 there exaggerated, as is the rolling of a ship at the 

 summit of its masts. But this was not all; the delicate 

 level indicated that when a strong wind was blow- 

 ing the bed-plate of the instrument was tipped up- 

 wards on the side from whence the wind was blowing, 

 indicating a leaning over of the mountain due to the 

 wind-pressure, as though the base of the mountain was 

 temporarily thrust downwards into the yielding cushion 

 of its rock -bed, on the side where the force of the wind 

 temporarily increased its pressure, i.e., on the side oppo- 

 site to that from which the wind was blowing. 



ASTRONOMY IN CHINA: THE PEKIN 

 OBSERVATORY. 



T^IG. 3 shows that for observations the Chinese astro- 

 ■*• nomers make use of a ladder on rollers, analogous to 

 those employed in European observatories, and moving 



upon a double rail. But we must not honour the Chinese 

 imagination for this improvement, for the ladder appears 

 of recent construction, so has probably been imported 

 from Europe. 



There are, further, upon the terrace an armillary 

 sphere, an equinoxial sphere, and a celestial sphere of 

 six feet in diameter (fig. 4). This last instrument 

 attracted the admiration of Father Lecomte, and is, in 

 fact, very remarkable. All the stars are shown in relief 

 in their proper places. It is so well suspended that a 

 child could turn it in the direction of the diurnal move- 

 ment, though it weighs 2,000 lbs. 



He describes the ornaments shown in the figure, and 



FiG.^3.— Observatory Ladder. 

 the concealed wheel-work which gives the axle any 

 desired inclination. 



One of the most remarkable instruments is the 

 gnomon, analogous to that used by Kuo-Shou King, 

 astronomer to the Emperor Kublai Khan, founder of the 

 first Tartar dynasty and creator of the first Tartar 

 dynasty. This astronomer used it for executing certain 

 observations, of which Laplace speaks in laudatory terms 

 in his Me'canique Celeste. 



In addition to the instruments just named, we figure a 

 very ancient armillary sphere dating back to the thir- 

 teenth century (fig. 5). The inevitable bronze dragons 

 supporting it are remarkable for their delicacy of execu- 

 tion. Father Verbiest effected a reorganisation of the 

 observatory in 1670, very near the time (1667) when 

 Dominic Cassini created the Observatory of Paris for 

 Louis XIV. He removed the instruments of Kuo-Shou 

 King, most of which still exist, and which have been 

 recently photographed. They differ from those of Father 

 Verbiest chiefly by their profusion of ornaments and 

 by being less easily handled. They are graduated in 

 365 degs., so that the sun traverses daily one of their 

 degrees. They are similar to those which Tycho con- 

 structed at his observatory in the Isle of Huen, with 



