u6 



SCIENCE-GOSSIP. 



analysts call attention to the fact that the dredgings 

 are more or less from the surface of the ooze, where 

 it must be full of newly-acquired carcases of dead 

 Foraminifera. Had it been possible to obtain 

 specimens for analysis from beneath the surface of the 

 ooze, where it had been longer exposed to chemical 

 action, the organisms would have been in a more 

 divided condition, and there would have been a 

 larger proportion of amorphous matrix. These oozes 

 in the present deep seas, at depths of between i,Soo 

 and 2,000 fathoms, may be held to possess a great 

 chemical and microscopic resemblance to chalk. 



We have now touched upon the results of this 

 famous deep-sea expedition, in so far as it is germain 

 to our subject. As may be imagined from the task 

 which was placed before it at the outset, a mass of 

 knowledge was collected, much of which is of intense 

 interest to the geologist, as showing the method of 

 deposition of strata, and especially of the gradual 

 building-up of organically-formed rocks. 



It will also be observed that the characters of the 

 Chalk which have been previously represented, agree 

 more particularly with those layers of globigerina 

 ooze which are found, more or less consolidated, 

 beneath the upper creamy surface, layer at the bed of 

 the Atlantic and other ocean areas. Generally speak- 

 ing Chalk has a specific gravity of from 2.4 to 2.6. 

 There is usually a small proportion of water contained 

 in it when fresh from the quarry, amounting to about 

 5 per cent., whilst there are generally, even in its 

 purest forms, traces of free silica and ferric oxide. 

 The silica is often present in greater proportions, 

 whilst in the red varieties of Chalk there is frequently 

 as much as 9.28 per cent, of silica and 9.6 per cent, 

 of oxide of iron, together with a little magnesia. 

 Alumina may be present in very varying proportions. 



It is a remarkable fact that the true Chalk is the 

 only formation of its kind throughout the whole 

 succession of geological strata. In this way we see 

 now-a-days in the deep ocean depths a certain kind of 

 formation accumulating, known as calcareous ooze, 

 leaving out of consideration for the moment the 

 siliceous ooze. This ooze bears the character of 

 modern Chalk. There is no reason why in former 

 times, over and over again, a similar calcareous 

 formation — a Chalk, should not have been accumu- 

 lating in the oceans of those days. Our hard white 

 Chalk stands out peculiarly alone, as the sole forma- 

 tion of its kind known to geologists. Yet we know 

 of no reason why there should not be a representative 

 Chalk in each of the fifteen great periods known in 

 ■the geological ages. The greater portion of the 

 stratified systems are marine in character : there are 

 a few fresh water, and rather more of estuarine 

 deposits. The marine strata, however, exhibit no 

 intercalated beds to show that they were formed so 

 far out at sea as to give rise to a calcareous ooze. It 

 is only when we come to cretaceous times we find 

 any trace of such a ooze. Mr. Jukes-Browne says it 

 is now generally acknowledged that the great mass of 

 the rocks which form our modern continents are such 

 as are nowformed only within 20dand 30omiles of land, 



and they very seldom include any deposits resembling 

 those now accumulating in the depth of the Atlantic 

 and Pacific Oceans. There is only one formation in 

 Britain, undoubtedly accumulated in deep water, at a 

 great distance from land of a continental character, 

 and that is the Chalk ( ' ). Therefore, with this one 

 exception, all the formations it is possible for the 

 geologist to examine, are such as have been formed in 

 a comparatively narrow area of 200 to 300 miles in 

 width around the lands of the various periods. Beyond 

 this area, we are unable to judge what forms of life 

 existed. 



Deep sea life is absolutely hidden from us until 

 Cretaceous times, and then we get a temporary glimpse 

 of life at a depth of 400 to 500 fathoms, or 2,400 to 

 3,000 feet. If, as Professor Hull maintains, the birth 

 of the Atlantic Ocean took place at the end of the 

 Carboniferous era, it would seem almost possible that 

 the Atlantic ooze has been in process of formation ever 

 since that epoch. Its eastern extension, including 

 those in the whole of Europe, has undergone a series 

 of oscillations which have caused the deposition of 

 post-carboniferous stratified Europe. Whilst in that 

 period which we call Cretaceous, the continent sank 

 deepest of all, until it constituted to all intents and 

 purposes a portion of the bed of the long-ago Atlantic 

 Ocean. 



It is now generally accepted that in the modern sea- 

 oozes we have the analogues of the Chalk deposits, and 

 it is fairly agreed that their rate of growth represents 

 the probable rate at which the Chalk itself grows. It 

 has been reckoned as an outside estimate, that 

 certainly not more than a foot of ooze accumulates in 

 a hundred years. If the ancient fossil ooze we call 

 Chalk, which, reckoning all its various stages, we may 

 estimate at a 1,000 feet thick, accumulated no more 

 quickly, we have a period of 10,000 years at least, 

 during which the Chalk Sea was in existence. Too 

 much stress must not, however, bejaid upon the period 

 mentioned as being in any way exact. There would 

 be local causes that might affect the rate of deposition. 

 The various platforms in the Chalk indicate changes 

 of conditions which would affect it. Further, certain 

 stages in the Chalk that appear in some parts, are un- 

 represented in others, whilst much of the chalky 

 ooze at one time laid down, has since suffered greatly 

 by denudation. The Chalk as we know it cannot be 

 the whole of what formerly existed. A hundred and 

 more years ago we find Gilbert White writing : " was 

 there ever a time when these immense masses of 

 calcareous matter were thrown into fermentation by 

 some -adventitious moisture ; and were raised and 

 leavened into such shapes by some plastic power ? 

 Perhaps I may be singular in my opinion, and not so 

 happy as to convey to you the same idea ; but I never 

 contemplate these mountains without thinking I perceive 

 somewhat analogous to growth in their gentle swellings 

 and smooth fungus-like protuberances, their fluted 

 sides, and regular hollows and slopes, that carry 

 at once the air of vegetative dilation and expansion." 

 White was an early geologist, but a much more recent 

 (l) The Building of the British Isles. A. J. Jukes-Browne. 



