Jan. 20, iSSS.] 



SCIENTIFIC NEV^S. 



67 



cumulus in a thunderstorm gave the idea in the Nor- 

 wegian Eddas that Thor's chariot was drawn by goats ; 

 while the drooping form of the same cloud, the festooned 

 cumulus, looked to the early Aryans as the udders of the 

 cows of Indra. The peculiar kind of cloud through which 

 the sun streams in apparently diverging rays of light was 

 also described, and in connection with it the lecturer read 

 the Pacific legend of Maui, who is related to have bound 

 the rising sun with slip-knotted ropes of cocoa-nut fibre 

 to prevent his too earl}' setting, the ra^'s, as seen in the 

 morning and evening, being described as "the ropes of 

 Maui." The appearance was best known in this country 

 as " the sun drawing water." The imagery which the 

 people .saw in the clouds depended on their attitude of 

 mind or on anj' prevailing excitement. Examples ot this 

 were given in the figure of an inverted crescent with a 

 sword through it, seen by the Turks at Vienna, the vision 

 of a kilted Highlander at Windsor on the eve of Culloden, 

 and the appearance of an Irish harp at North Berwick in 

 September last. So long as cloudland was peopled by 

 terrib'e beings, the tendency of that attitude of mind was 

 to make men afraid. The productions of the poets in- 

 tensified this feeling. Modern meteorology, on the con- 

 trary, conjured up the picture of a sea of vapour-laden 

 air eddying in a ver}^ limited number of waj^s, and de- 

 veloping an equallj'' limited number of cloud-structures. 

 Man lived at the bottom of that atmospheric ocean, and 

 he was now learning to utilise the indications of clouds 

 for his own benefit. The moral effect of weighing and 

 micasuring, as, for example, the waves of the sea, was en- 

 tirely destructive of vague terrors. Modern science was 

 not merely the collection of facts, but the means of build- 

 ing up that attitude of mind which raised man to a higher 

 level, instead of prostrating him before the creatures of 

 his own imagination. 



BIRMINGHAM AND MIDLAND INSTITUTE. 

 A LECTURE was given by Professor Darwin on " The 

 Ring of Saturn." The object of his lecture was to give 

 an account of the investigations by which it has been dis- 

 covered how that ring is built up. His reason for 

 selecting this subject for his discourse was the desire of 

 rescuing from unmerited neglect one of the discoveries of 

 a French astronomer and mathematician, M. Edouard 

 Roche, who died in 1883. It might easiij- be imagined, 

 he said, that so extraordinary an appendage as a flat ring 

 has excited amongst astronomers abundant speculations as 

 to its constitution, its history, and its future fate. As is 

 usually the case, what we now confidently believe to be 

 the truth has onlj' been reached bj- degrees. Herschel 

 thought that the ring was solid because it shone so 

 brilliantljf, and Laplace investigated the shape which 

 such a solid ring must have, if it is not to break in pieces, 

 and if it is to continue to revolve about the planet. Fifty 

 years after Roche, in treating a problem of abstract 

 celestial mechanics, arrived indirectly at a most interest- 

 ing conclusion concerning Saturn's ring. The lecturer 

 then proceeded to give an account of Roche's paper. 

 He first explained that the attraction of the earth on the 

 moon is such that the moon is not perfectly spherical, 

 but that her body protrudes towards the earth ; so that 

 she is slightly egg-shaped, with the long axis of the egg 

 pointed towards the earth. If the moon revolved round 

 the earth nearer than she actuallj" does the elongation of 

 the egg would be more pronounced, and if she were very 

 near to the earth her body would be so much elongated 

 that she could not continue to cohere together, but would 



break up into globules. Roche then succeeded in dis- 

 covering the utmost limit of the elongation which the 

 moon or any satellite can endure, and how far from the 

 planet the satellite is when thus elongated. An egg- 

 shaped model was exhibited to show this extreme limit 

 of elongation. Roche proved also that the satellite when 

 in this condition is at a distance of two and eleven 

 twenty-fifths of the planet's radius from the planet. This 

 distance the lecturer called Roche's limit. The meaning 

 of this is that if a lump of matter were set to circulate 

 round a planet at less than two and eleven twenty-fifihs 

 of a planet's radius from the planet, then the forces to 

 which it would be subjected are such that it would be 

 rent in pieces. Roche's limit for Saturn is found to coin- 

 cide almost exactly with the outside edge of the ring, and 

 hence the conclusion is arrived at that the ring consists 

 of rocks, dust, and fragments, circulating independently 

 round Saturn. This, then, is the constitution of Saturn's 

 ring, and since the date of Roche's paper was 1848, in 

 justice to him the discovery in question ought to be 

 dated from that year. Roche's work, however, passed 

 unnoticed, even up to the present time, and it was not 

 until nine years later that the same discovery, announced 

 by Maxwell, of Cambridge, commanded the general 

 attention of men of science. Maxwell's essay formed a 

 masterly discussion of the mechanics of Saturn's ring, 

 and he was recognised as the chief authority on the sub- 

 ject. In conversation he used to describe the ring as a 

 " shower of brickbats," and he showed that the inevitable 

 collisions between " the brickbats " would, in some long 

 but indeterminate period of time, bring about the de- 

 struction of the system of rings. 



ROYAL SCOTTISH SOCIETY OF ARTS. 



At a meeting held in Edinburgh on December 12th, Mr. 

 W. D. Cay, C.E., read a paper on the construction of 

 marine works with concrete bags, and the plant used for 

 their deposit. He noticed some previous cases of the use 

 of sacking in the laying of concrete foundations. The 

 use of sacking bags, however, had been first introduced 

 by himself at the building of the Aberdeen breakwater. 

 There the concrete bags had been dropped into position 

 by means of a hopper barge. The barge was fitted wih 

 bottom doors. When in use her hold was lined with 

 jute sacking, the concrete was then filled in and the sack- 

 ing sewed up. The barge was towed into position, the 

 bottom doors were opened, and the concrete bags dropped 

 down into position, fitting accurately over each other. 

 The barge used at Aberdeen carried fifty tons of concrete, 

 and barges carrying a hundred tons had since been used. 

 The breakwater at Aberdeen had now stood twelve 

 years, and it had been reported this year that it had re- 

 quired but fifty pounds to keep it in repair since that 

 date. Mr. Cay also described the dropping into the water 

 of concrete bags from boxes or skips carried by cranes, 

 in which the arrangement of bottom doors was the same. 



NORTH OF ENGLAND INSTITUTE OF MINING 



AND MECHANICAL ENGINEERS. 

 A MEETING of this Institute was held on December lo'h, 

 Sir Lowthian Bell (President) being in the chair. 



The Secretary read the report of the committee ap- 

 pointed to inquire into the observations on earth tremors, 

 with a view to determine their connection, if any, with 

 the issue of gas in mines. Experiments with a seismo- 



