488 



NATURE 



[March 21, 1901 



nature of the bottom. A new map shows the distribution 

 of deposits in the North Atlantic according to recent in- 

 formation, and an inset, based principally on the 

 soundings of the Britannia, shows the outline of the 

 Azores bank. 



The lines of soundings fall naturally into three groups ; 

 those between the Azores and the British Islands, those 

 between the Azores and North America, and those on 

 the Azores bank. In each case new discoveries of interest 

 have been made. On the first line a new depression, 

 with soundings over 3000 fathoms, the " Peake deep," 

 has been found ; but the chief feature is the discovery 

 of numbers of shoals rising steeply from over 2000 

 fathoms to within 1200 and 1400 fathoms of the surface, 

 evidently the summits of submarine cones. The more 

 southerly of the two lines between the Azores and North 

 America revealed the important fact that the " tail " of the 

 great Newfoundland bank extends much farther south 

 than has hitherto been supposed. The Britannia has 

 added largely to Thoulet's chart of the Azores bank, but 

 the ground is so irregular that much sounding still 

 remains to be done ; the bank is described as being pro- 

 bably " a series of small hills, no doubt due to volcanic 

 action." 



The observations of bottom temperature, which were 

 made with thermometers of Six's pattern, consist of two 

 series of parallel lines, one double line between the Azores 

 and the British Islands, and another between the Azores 

 and America. It is pointed out that, on the whole, these 

 observations give temperatures above the mean assumed 

 in the Challenger report for this region of the ocean ; 

 but as that value is merely the average of the observa- 

 tions existing at the time, the volume of water at different 

 temperatures not being taken into account, the difference 

 may not be due to actual change. On the other hand, 

 the Britannia observations show that in each of the 

 double lines the temperatures are different ; of the Azores- 

 America line, the more northerly gave the higher readings 

 at depths below 2000 fathoms ; of the Azores-Europe line, 

 the more southerly. It is suggested that these differences 

 are due to actual change occurring between the dates of 

 observation, and this view is supported by reference to the 

 different temperatures observed in the south-west Pacific 

 by H.M.S. Egeria in 1889 and H.M.S. Penguin in 1897. 

 From the observations of H.M.S. Jackal in 1893, the 

 writer showed that in the Fasrce-Shetland Channel tem- 

 perature was not constant at depths of at least 400 

 fathoms, and it was further shown that the variations 

 were due to differences of level in the movements of 

 water. The results of more recent work go to show that 

 the active circulation of the eastern and western Atlantic 

 consists chiefly of stream currents comparatively near 

 the land, developed by the drift movements of the central 

 areas and altogether separated by them. The currents 

 on the eastern side are chiefly caused by the banking up 

 of water from the west-wind drifts, and while most of this 

 water escapes laterally to north and south, there is also 

 a descending movement — hence the high temperatures 

 in the depths. It is known that the horizontal streams 

 are liable to great variations, partly seasonal, partly 

 irregular, and the observations of the Britannia seem to 

 prove that the vertical movements undergo corresponding 

 changes. The variations of temperature may be regarded 

 NO. 1638. VOL. 63] 



as directly due to movements of water, and therefore as 

 seasonal in only a secondary sense, if at all. 



The samples of deposits collected by the Britannia^ 

 numbering 432, are very fully described by Sir John 

 Murray. The map shows two considerable alterations 

 when compared with that of the Challenge} report. First, 

 the red clay area is extended northward from the deep 

 water round Bermuda and passes directly into the blue 

 mud south of Newfoundland. This abrupt transition to a 

 terrigenous deposit is accounted for by the great distance 

 to which continental detritus is carried by icebergs. 

 Second, the pteropod ooze region round the Azores is 

 restricted to a smaller ai-ea than before, although it is noted 

 that the characters of this deposit are not well marked, 

 and that it is difficult to classify some samples as pteropod 

 or globigerina with certainty. Many samples from 

 moderate depths near the Azores contain fewer pteropods 

 than those obtained from deeper water farther north. 



H. N, D. 



OUR BOOK SHELF. 



Modern Astronomy. Being some Account of the Astro- 

 nomical Revolution of the last Quarter of a Century. 

 By H. H. Turner, F.R.S. Pp. xvi-l-286. (West- 

 minster : Archibald Constable and Co., Ltd., 1901.) 

 Price 6s. net. 



The Savilian professor is so strongly impressed with the 

 magnitude of the changes which have taken place in 

 astronomical methods during the last quarter of a 

 century that he does not hesitate to describe them as 

 revolutionary. The task which he has set himself in 

 this book is to give a brief review of the present situa- 

 tion, pointing out the nature of the changes rather than 

 giving a complete account of them or of the discoveries 

 to which they have led. The book can thus in no sense 

 be regarded as a reference or text-book, but it may be 

 remarked that elementary explanations have usually been 

 introduced to make the matter generally intelligible. 



Several quotations are given as an indication that 

 about 1875 there was a feeling that novelties in astro- 

 nomical methods or results were no longer to be expected. 

 Such a feeling, if it existed, was certainly premature. 

 New instruments of precision have been invented or 

 erected ; telescopes of increased size and novel construc- 

 tion have been made ; photography has come to aid the 

 astronomer in numberless ways ; astrophysics has become 

 an important branch of the subject, with almost bound- 

 less possibilities ; and even in mathematical astronomy 

 new methods of treating the lunar and planetary theories 

 have been introduced. 



This progress is treated under the four heads, 

 "Modern Instruments," "Modern Methods," "Modern 

 Results " and " Modern Mathematical Astronomy." 

 Occasional overlapping and repetition is the natural out- 

 come of this classification, but the book provides an 

 interesting and fairly connected account of several de- 

 partments of astronomical work. The treatment of 

 astrophysics, however, leaves much to be desired. There 

 is practically nothing in the book relating to the great 

 advances in our knowledge of the sun as a result of 

 recent eclipse work, and it is especially to be regretted 

 that the evidences of stellar evolution are not more fully 

 set forth. There are other indications of the author's 

 unfamiliarity with the progress of astrophysics ; on p. 239, 

 for instance, he states that no supposition allied to that 

 of a revolving companion will explain the variability of 

 stars in clusters, whereas the collisions of revolving 

 swarms of meteorites at periastron explain the light 

 curves completely. For the sake of historical accuracy. 



