Oceanographic Abstracts 7 4 l

de la qualit~ m~me des argiles, surtout illitiques, sur lesquelles le milieu marin n'est capable d'agir, semble-t-il, que par une rOgularisation des r~seaux.

Nous notons cependant que les assemblages interstratifi~s irr6guliers, presents en faible quantit6 montrent une certalne tendance ~t 6voluer vers l'illite, au contact des eaux salves. Nous sommes tent*s d 'at t r ibuer ~t ce fait une cause chimique, tel le garnissage des feuillets par les ions potassium de l 'eau de mer. La t~nuit6 de phOnomOne engage cependant ~t la prudence, et on peut se demander si d 'autres facteurs que ceux introduits par le millieu chimique n ' interviennenet pas. Le facteur hydrodynamique agit peut-~tre par un tri granulomOtrique, ou la taille des lamelles argileuses par la modification des propriOtOs physiques d'expansion. Le phOnomOne observ6 nOcessite, ~ cause de sa discrOtion, une 6rude plus approfondie, tant de larigueur de l'expOrimentation que que du milieu chimique environnant les sediments.

CHAa"rOPADHYAY N. N., 1964. On the effect of continuous diffusion of salt nuclei into the atmosphere on local rainfall, lnd. ,r. Met. Geophys., 15 (3): 381-392. It is generally recognised that the presence of salt nuclei in clouds has a powerful influence on rain formation. With a view to finding out whether continuous diffusion of salt nuclei into the air from a powerful atomizer, placed at a height of 60 ft above ground, which is fed by salt solution and worked by compressed air at 20 atm would have any effect on local rainfall, experiments were undertaken at the J'adavpur University in 1958 and 1959. The atomizer was kept in continuous action throughout daylight hours during April to October in 1958 and during July to October in 1959.

During 1958 and 1959 West Bengal had deficient monsoon rainfall. The departures of rainfall from the normal in each of the months, during which the experiments were done, were plotted and the lines of equal departures were drawn. These showed that the curves of least negative departures and in some cases highest positive departures were generally oval-shaped extending from north of Calcutta to a distance of about 100 miles towards the prevailing wind direction, in all the months in which the experiments were done. This suggested that this oval-shaped area received more rainfall than the neighbouring proportion of which reached cloud levels after a travel of short distance from south Calcutta, it is considered that this factor may have contributed to the increase in rainfall.

CRAVE K. E. and B. D. WrmeLZR, JR., 1965. Mineralogi~ changes during growth in the red alga, Clathromorphum compactum. Science, 147 (3658): 621. The amount of magnesium in the skeletal calcite of the encrusting marine red alga, Chlathromorphum compactum varies s~asonally in response to changes in water temperature. X-ray diffraction analyses of serial samples of this alga collected in the Gul f of Maine indicate more than a 40 per cent change in composition during a year and demonstrate a more rapid calcification during warmer periods.

CHAYr.s F. and D. VELDE, 1965. On distinguishing basaltic lavas of circurn-oceanic and oceanic- island type by means of discriminant functions. Amer. d. Sci., 263 (3): 206-222. The basaltic lavas of the oceanic-island environment are much richer in t i tania than those found on the landward flanks of the great deeps margining the open oceans. Exceptions to this rule are rare; examination of a large body of data indicates tha t the efficiency of a classification based solely on TiO~ content would be nearly 93 per cent. Neither any other single oxide nor any unweighted combination of oxides other than TiOz approaches the efficiency of TiO~. Extensive discriminant functions calculations indicate :

1. Weighted linear combinations which include Tie2 may be slight improvement over TiO~ alone.

2. Any combination of oxides which does not include Tie2 is far less effective than Tie2 alone.

Cvlr.SsEt.rr R. and C. LnLou, 1965. ROle du " d & r i t u s " dans la fixation de radioOlOments dans le milieu matin. C. R. Acad. Sci., Paris, 260 (4): 1225-1227. Le rOle du ' d e t r i t u s ' comme tr~s important agent de conceptation de certains radio~lOments artificiels prO'sents d a m le milieu mat in tels que les cOriums 141 et 144, le pras~.dyme 144, les rutheniums 103 et 106, le rhodium 106, le zirconium 95 et le niobium 95, a 6t6 mls en 6vidence. Le dOtritus servant en particulier de nourriture ~t la laurie benthique peut jouer un rOle essentiel darts le transfert de la radioactivit6 d a m la chaine alimentaire.

CLAY C. S. and P. A. RONA, 1965. Studies of seismic reflections from thin layers on the ocean bot tom in the western North Atlantic. d. Geophys. Res., 70 (4): 885-869. Ssismic reflection profiles were made of shallow, sub-bottom reflectors in three different physio- graphic provinces of the Nor th Atlantic. In the Hatteras abyssal plain at 32 ° 42'N, 71 ° 30'N, a layer 0.16 km thick with velocity of about 1-7 kin/see was observed. The reflections from the thin sediments in the Blake-Bahama basin were too irregular for interval velocity analysis. Two reflecting layers on the crest of the outer ridges at 29 ° 42'N, 73 ° 23'W, were observed at 0.06-kin and 0-11-kin sub-bottom depths. Interval velocities were measured to be 1.4 kin/see for the upper layer and 1.6 kin/see for the lower layer. Errors are estimated to be of the order of 4- 0.2 kin/see. F rom the character of the outer ridge reflection profiles the sediments appear to be uniform laterally over distances of several kilometres.