10 



KNOWLEDGE & SCIENTIFIC NEWS. 



[Feb., 1 904. 



The experimental models, by which mountain-structure is 

 made to arise in circular circumscribed areas, are of wide 

 interest (pp. 131-215), and lead to some criticism of the views 

 of Suess on the potency of differential subsidence to produce 

 the oceanic depths and the high continental masses. 



Chapter XIX., on Slaty-Cleavage, descends somewhat from 

 geomorphology to petrology; the interestinj; details have been 

 already pul)lished by the Liverpool Geological Society. The 

 volume also contains a paper on the denudation of America, in 

 which the relations of continents and oceans are again dis- 

 cussed; and a final and lucid statement of the case against 

 those who have asserted the permanence of these larger 

 features of our globe. 



The geological reader and the librarian will not consider the 

 price of Mr. Keade's book high, when once they have turned 

 it over, and have noted the numerous original ilhistrations. 

 which in themselves give it a permanent value. 



Galileo: His Life and Worli, l\y J.J. Fahie. (London: John 

 Murray, Albemarle Street, W., UJ03 ; i6s. net.) Mr. I'"ahie 

 has succeeded in giving a very life-lilic and attractive 

 picture of the great philosopher. His restless energy of 

 investigation, his keenness of observation, his affection and 

 generosity to his relatives and friends (many of whom were 

 most undeserving), and the biting wit with which he attacked 

 his enemies are brought vi\idly before us. The last named 

 (|uality was his ruin, and, far more than any novelty or heresy 

 in the doctrines be taught, brought upon him the bitter perse- 

 cutions from which he suffered. His real crime was that he 

 made his opponents a laughing-stock, and Pope Urban \Tn, 

 believed that he too had been " made game of." He had 

 given Galileo an argument against the proof which Galileo 

 considered the most cogent in establishing the motion of the 

 earth round the sun. Galileo placed that argument in the 

 mouth of Simplicio, the representative of the Ptolemaic 

 philosophy in the great " Dialogue," and the Pope regarded 

 this as equivalent to saying that he was a " simpleton." 

 Curiously enough this same irrefragable proof — the argument 

 from the tides — is untenable, so that the Pope's objection has 

 been justified by the result, though his mode of reasoning was 

 unscientific. 



Galileo's attitude of mind towards science was quite different 

 from that of his contemporaries. As a result of this, his life 

 was one of brilliant scientific triumphs, but also of unceasing 

 conflict and bitter suffering, relieved, however, until the last 

 eight years of his life, by the touching and romantic devotion 

 of his noble-hearted daughter, \'irginia. His is a heroic 

 figure, and it as a hero that Mr. Fahie has treated him ; the 

 one fault to be found with his portrayal of him l)eing that, like 

 the Aristotelians of Galileo's day, he will not allow that there 

 can be any spots on his sun, for he supports Galileo where 

 he least deserves support, namely in his refusal to allow any 

 merit to rival and independent workers in the same fields, such 

 as Lippershay, Scheiner, and Marias. 



The SoLltness of the 

 Deocd Sea. 



Two causes, says Mr. William Ackroyd, in the report of 

 the Palestine Exploration Fund, have been assigned to 

 account for the saltness of the Dead Sea. The first of 

 these is the accumulation of chlorides, which soh-ent 

 denudation derives from the rocks of the Holy Land. 

 The second e.xplanation is that an arm of the Red Sea 

 was cut off by the rising of Palestine in prehistoric a^es, 

 and in either or both cases the saltness would have been 

 intensified by evaporation. 'J'here remains, however, to 

 be taken into consideration a third cause — the atmo- 

 spheric transportation of salt from the Mediterranean. 

 This may not improbably be a more potent factor than 

 either of the other two causes of the Dead Sea's saltness. 

 The salt which the winds carry inland from the sea falls 

 in rain and is carried back again to the sea; but in the 



case of an inland lake without outlet it remains for evapo- 

 ration, so much so that in the case of a Pennine reservoir 

 water equally salt with that of the Dead Sea would be 

 produced by this means in a fraction of the time usually 

 assigned to the Pleistocene Age. Taking specimens of 

 the rocks on which Jerusalem is built as samples of the 

 Palestine rocks, they are found to be limestones of 

 various compositions, and with the one exception of Kakule 

 limestone, which contains 0-025 per cent, of chlorine, or 

 o'04.i of common salt, the chlorine contained in these 

 rocks approximates to the general average of that found 

 in the limestones of other countries of o-oi per cent. 

 This percentage would be quite inadequate to account 

 for the salt in the Dead Sea, and the salt yielded to 

 rivers by denudation is not a ninety-ninth part of that 

 which has been supplied by rain water. Nor would the 

 saltness of the Dead Sea be fully accounted for if a marine 

 area had been cut off during the rising of the land, as the 

 initial saltness thus acquired would only be about a 

 fourth of that subsequently attained to ; and, moreover, 

 in this condition of saturation it has been for an unknown 

 length of time continually precipitating its excess of salt. 

 The intensity of meteorological conditions in the past 

 geological history of Palestine have been much more 

 severe than those now obtaining, and the atmospheric 

 transportation of salt would be correspondingly greater. 

 Some of the salt then accumulated has been left by the 

 dwindling waters of the Dead Sea in areas to the north 

 and south, notably in Jebel Usdum, and the highly 

 brackish rivulets which come from these neighbourhoods 

 now are but contributing again what long ago came from 

 more distant sources. 



The Nebulosities round 

 / Cygni. 



];y Dr. Max Wolf, F.R.A.S. 



1 DISCOVERED these large nebulous masses in iSgi.andon 

 several occasions have published photographs of them. 

 Some two and a half years ago I was fortunate enough 

 to get a fairly good picture of them with my sixteen 

 inches Brashear lens, which I hope may prove of interest 

 to the readers of" Knowledge & Scientific News." The 

 accompanying plate has been made from a contact print 

 from the original photograph, which was exposed for 

 nearly seven hours, on the nights of July 16 and 17, igoi. 



The bright star involved in nebulosity in the centre of 

 the plate is y Cygni. The star, a Cygni, is not included 

 in the plate, but would lie a little outside it, at the left 

 upper corner. The nebulous stream running diagonally 

 across the plate, in the line joining y Cygni and a Cygni 

 is very distinctly shown. But the most striking feature 

 of this region is furnished by the broken nebulosities 

 near the centre of the plate. The contrast, too, afforded 

 by the crowds of stars and the nebulous masses is very 

 remarkable. In some places all are mixed together, 

 bright stars, small stars, and nebulosity ; whilst in others 

 the intervals between the stars are entirely free from nebu- 

 losity. Very striking, too, are the irregular dark holes in 

 the nebulosity to the west of 7 Cygni, and the clouds to 

 the east, and north-west of that star. A curious straight 

 line of stars crosses the plate north of the centre. 



The scale of the plate is 32 millimetres to one degree 

 of arc. 



