April 21, 1889] 



NATURE 



607 



Tertiary Chalk in Barbados. 



In a previous communication (Nature, February 14, p. 367) 

 we called attention to the series of oceanic deposits in Barbados, 

 of which the well-known Radiolarian earth (or Polycistina marl) 

 forms a part. We stated that these deposits had a wide exten- 

 sion, and were of variable composition, soone being much more 

 calcareous than others ; and further that nhey formed an inde- 

 pendent series, resting unconformably on the older clays and 

 sandstones which are supposed to be of early Tertiary age. 



Since the date of our former note, we have examined many 

 sections along the outcrop of the deposits, and find that the 

 varieties which we had noticed fall into a natural succession, the 

 calcareous earths lying principally at the base, though in the 

 northern part of the island there is a development of similar beds 

 at the summit. The total maximum thickness is about 200 feet, 

 and the series contains many interesting varieties of rock. We 

 hope to describe these at length, and to lay our results before the 

 Geological S jciety, but as some time must elapse before this can 

 be done, we write at once to place on record the fact that some 

 of the beds have all the essential characteristics of typical 

 (Cretaceous) chalk. 



We have samples which consist of from 80 to 90 per cent, of 

 calcium carbonate, which give the usual white streak of chalk, 

 which contain Foraminifera in abundance, and have a minute 

 structure which can hardly be distinguished from that of certain 

 l)ortions of the English chalk. A thin slice examined under a 

 I -inch objective shows many Foraminifera distributed through a 

 matrix which under this power appears to be amorphous ; the 

 Foraminifera are chiefly Globigerinae of the thick-shelled type 

 similar to that figured in Carpenter's " The Microscope and 

 its Revelations," sixth edition. Examined under a higher 

 power the matrix can be resolved into definite particles, among 

 which can be distinguished many forms identical with the so- 

 called crystalloids of the ch.ilk. Our friend Mr, W. Hill, to 

 whom we sent a specimen of this Barbadian chalk, says it pre 

 sents a very close analogy to our English chalk. Other samples 

 combine the characters of chalk and Radiolarian earth having 



a calcareo-siliceous matrix containing a mixture of Radiolaria and 

 Foraminifera. 



We believe that the Barbadian depjsits were formed on the 

 floor of the Atlantic previous to the upheaval of the Caribbean 

 Islands, and this cjnclusion is strengthened by the fact that 

 similar Radiolarian earths occur in Trinidad and Hayti. We find 

 too that the late Dr. Carpenter remarked that if the modern 

 oceanic oozes were uplifted they would form deposits similar to 

 the Barbados earths ("The Microscope and its Revelations," 

 sixth edition, p. 602). 



We wish to correct one paragraph in our former letter, in 

 which we tacitly assumed that the Caribbean Islands were 

 originally part of the American continent, and were therefore 

 continental islands ; we are now disposed to regard Barbados at 

 any rate as an oceanic island, and believe that it has never been 

 connected with South America since its upheaval as an island. 

 Colonel Feilden has collected some evidence on this point which 

 we hope he will shortly publish. We may state that the nearest 

 island to Barbados (St. Vincent) is one hundred miles to the 

 west, and that the intervening sea is more than 1000 fathoms 

 deep. 



But whether classed as an oceanic or a continental island, the 

 rocks of Barbados are equally interesting to the physical geologist, 

 since they give proof of a complete interchange of continental and 

 oceanic conditions in Tertiary times ; for the underiying sand- 

 stones and shales imply the close proximity of a continent 

 during their formation, while the chalky series proves the sub- 

 sequent conversion of this shallow sea into an oceanic area. 

 Moreover, the existence of both sets of rocks now at the surface 

 is entirely antagonistic to the prevalent theories respecting both 

 continental and oceanic islands, 



A T. Jukes Brow.ne. j 

 \pril 22. J. B. ilARRISO.V. I 



A New Mountain of the Bell. 

 I HAVE just returned from a journey of four weeks in the 

 desert of Mo'mt Sinai, made with the especial object of studying 

 the Jebd Nagous in connection with the joint researches of 

 Dr. Alexis A. Julien and myself on "musical sand." The 

 " Mountain of the Bell " is situated on the Gulf of Suez, abjut 

 four and a half hours from Tor by the roundabout camel rotUe. 

 It was first described by Seetzen in 180S, since which time it has 

 been visited by Ehrenberg, Gray, Wellstedt, Riippell, Ward, 



Newbold, and the late Prof. Palmer, as well as by large numbers 

 of pilgrims. My observations confirm in the main their accounts 

 of the acoustic phenomena heard, but my measurements differ 

 widely from those of all the travellers save Prof Palmer. 



The name Jebel Nagons is given by the Bedouins to a 

 mountain nearly three miles long and about 1200 feet high, 

 composed of white sandstone bearing quartz, pebbles, and veins. 

 On the western and northern sides are several large banks of 

 blown sand, inclined at high angles. The sand on one of these 

 slopes, at the north-west end of the mountain, has the property 

 ! of yielding a deep resonance when it slides down the incline 

 I either from the force of the wind, or by the action of man. 

 This bank of sand I distinguish from the others by calling it the 

 Bell Slope. It is triangular in shape, and measures 260 feet 

 across the base, 5 to 8 feet across the top, and is 391 feet 

 high. It has the high inclination of 31" quite uniformly. It 

 is bounded by vertical cliffs of sandstone, and is broken towards 

 the base by projecting rocks of the same material. The sand is 

 yellowish in colour, very fine, and possesses at this inclination a 

 curious mobility which causes it to flow when disturbed, like 

 treacle or soft pitch, the depression formed being filled in from 

 above and advancing upward at the same time. The sand has 

 none of the charac'.eristics of sonorous sand found on beaches. 

 When pulled downwards by the hands or pushed by the feet a 

 strong vibration is felt, and a low note is plainly heard re- 

 sembling the deep bass of an organ-pipe. The loudness and 

 continuity of the note are related to the mass of sand moved, 

 but I think that those who compare it to distant thunder 

 exaggerate. The bordering rocky walls give a marked echo, 

 which mny have the effect of magnifying and prolonging the 

 sounds, but which, as I afterwards demonstrated, is not essential. 

 There are no cavities for the sand to fall into, as erroneously 

 reported. The peak of Jebel Nagous rises above the Bell 

 Slope to the height of 955 feet above the sea-level, as determined 

 by a sensitive aneroid. 



After studying the locality and phenomenon for several days, I 

 farmed the opinion that it could not be unique as hitherto 

 supposed, and accordingly I tested every steep slope of blown 

 sand met with on the caravan route northward to Suez. On 

 April 6 I examined a steep sandbank on a hillock only 45 feet 

 high, and was rewarded by the discovery of a second Nagoiu. 

 This new Nagous is in the Wadi Werdan, only five minutes 

 o.T the regular caravan route, and one and a half days, by 

 camels, from Suez. The hillock is called by the Bedouins 

 Ramadan, and forms the eastern end of a range of low hills about 

 one quarter of a mile long ; being the only hills in the Wadi, 

 the locality can easily be found by travellers. The hills consist 

 of conglomerate and sandstone, and to the west of gypsum ; 

 they slope up gradually fr jm the north and end in bold cliffs on 

 the south side. Sand blown by the north wind is carried over 

 the cliffs, and restson the steep face at two inclinations, 31" above, 

 and 21 \ or less, below. By applying the usual tests with the 

 hands to the fine-grained sand, I found that wherever it lies at 

 the requisite angle to produce mobility (31^), it yielded the bass 

 note, though not so loud as on the Bell Slope of Jebel Nagous. 

 j In one instance, my friend and fellow traveller, Mr. Henry A. 

 I Sim, of the Madras Civil Service, who kindly aided me in ray 

 j investigations, heard the sound while standing lOO feet distant. 

 I The Nagous sand occurs at intervals throughout the 500 yards of 

 , low clifts ; the main bank at the east end being 150 feet wide 

 j and 60 feet high measured on the incline. I surred up the 

 mobile sand pretty thoroughly on this slope, and the next day it 

 , failed to give the sounds, not having recovered its properties. 

 I The intervening night was very cold (53°). I feel confident that 

 this phenomenon is not very rare in the desert, though the spon- 

 taneous production of sounds by sliding of the sand without 

 man's agency, as at Jebel Nagous, may be. Whether the Rig-i- 

 Raivan, north of Cabul, is caused by similar con liiions remains 

 to be determined, but I fear that the peculiar relations existing 

 between England and Russia will prevent my visiting Northern 

 Afghanistan. The Bcdoui.is who accompanied us were greatly 

 astounded at my discovery of a new Nagou-, and I fear that 

 their faith in a monastery hidden in the heart of Jabel Nagous 

 has received a severe shock. It is interesting to note that the 

 Nagous or modern gong is in daily use in the Monastery of St. 

 Caiherine, Mount Sinai, 



1 made photographs of Jebel Nagous and vicinity, as well as 

 of the new Nagous, and collected specimens of the rocks, sand, 

 &c. This communication must be regarded ns a preliminary 

 notice, full details being reserved for the work on "Musical 

 Sand " in preparation by Dr. Julien and myself. 



