94 



NATURE 



[September 19, 19 12 



is reasonable having regard to the restricted range of 

 their employment and the greater chance of external 

 help in case of accident. 



What remains to be demonstrated — and the task 

 will not be an easy one — is whether the large number 

 of lifeboats now thought to be essential can possibly 

 be so carried as to be loaded and got into the water 

 safely within a reasonable time after an accident has 

 taken place — say within half an hour or an hour. 

 Judging by the Titanic — in which case all the circum- 

 stances were most favourable to the loading and 

 lowering of boats — radical changes will be required in 

 the installation of lifeboats and in the means of lower- 

 ing them, if this essential condition is to be fulfilled. 

 All that need be added is that whatever may be the 

 number of lifeboats carried, and however efficient may 

 be the details of the arrangements for lowering these 

 boats, it is obviously of primary importance to secure 

 efficient watertight subdivision in passenger ships, so 

 as to minimise the risk of foundering and to lengthen 

 out the time which ships will remain afloat in cases 

 of accidents so serious as to involve their final sinkage. 

 On this matter another committee is still at work, 

 and no action can be taken by the Board of Trade 

 until its report has been presented. 



ATMOSPHERIC PRESSURE AND 

 TEMPERATURE. 



IN Aus dem Archiv der deutschen Seewarte, 191 1, 

 No. 4, W. BrockmoUer discusses the geographical 

 distribution of the monthly range of oscillation of the 

 barometer. So far as the southern hemisphere is 

 concerned, the question was thoroughly investigated 

 by Dr. VV. J. S. Lockyer in a recent publication of 

 the Solar Physics Committee, but Herr Brockmoller's 

 treatment of the subject covers a wider area, and 

 is based on a different definition of the "range." 

 He takes as the measure of this the mean value of the 

 difference between the highest and lowest barometer 

 readings for each month, and deals with a selection 

 of stations, about 300 in all. After correcting the 

 values for the periodic semi-diurnal variation, and for 

 height above sea-level in the case of a few high-level 

 stations, he plots the values for winter (December- 

 February), and for summer (June-August), and obtains 

 two very interesting charts, showing the isobarometric 

 lines, or lines of equal range. For the northern 

 hemisphere he obtains also normals for different lati- 

 tudes, and draws the isanomalies, or lines of equal 

 departure from normal. The range is least, 3 or 

 4 mm., in the equatorial region, and greatest near the 

 arctic circle, apparently diminishing again towards the 

 pole. The outstanding features are the maxima, in 

 both seasons, near Iceland and the Aleutian Islands, 

 the regions of the "permanent cyclones." The maxima 

 are naturally much less intense in summer than in 

 winter. Perhaps even more remarkable is the large 

 value of the anomaly on the east coast of North 

 America, where it is greater than at any other place. 

 The effect is possibly due to the proximity of the 

 division between the Labrador current and the warmer 

 water of the North Atlantic, but it is deserving of 

 further investigation. 



In the same journal. No. 5, Prof. Koppen and Dr. 

 VVendt discuss the vertical distribution of tempera- 

 ture over Hamburg between the earth's surface and a 

 height of 3000 m. The records obtained in nearly 

 1200 ascents of kites and balloons during the years 

 1904-C) have been analysed very thoroughly, and a 

 new departure has been made in the special treatment 

 of so-called inversions of temperature-gradient. The 

 authors find that such inversions occur in 6g out of 

 NO. 2238, VOL. 90] 



every 100 ascents, the temperature remaining constant 

 or increasing with altitude. Inversions are most fre- 

 quent in autumn and winter, and in December they 

 are found in nearly every ascent. At all seasons they 

 occur most frequently with southerly winds. Inver- 

 sions in which the increase of temperature exceeds 

 3° C. are almost invariably accompanied by a decrease 

 in the relative humidity except for those which occur 

 in the layer between the earth's surface and 

 a height of 500 m. At all seasons the sky is 

 more frequently cloudy than clear on the occasions 

 when inversions are recorded, but in spring and 

 autumn the number of cases of clear sky is large. 

 The clouds were found usually to have their lower 

 surfaces below 500 m., except in those cases in 

 which inversions occurred beloxv 500 m. Another 

 section of the paper deals with the dependence of 

 temperature-gradient on wind direction. Near the 

 surface the gradient is greatest with N. winds, above 

 500 m. with W. winds, and above 1000 m. with 

 .S.W. winds. As the wind usually veers with increas- 

 ing height, it seems probable that the actual direction 

 of the current for maximum gradient in the layer 

 considered will be northerly at all heights. 



PLANKTON INVESTIGATIONS. 



IN the Bulletin Trimcstriel, 191 1, the second part 

 of the " R^sum^ des Observations" continues the 

 summary of the plankton investigations carried out 

 under the international programme in the north-east 

 .'\tlantic and north-west European waters during the 

 years 1902-8. The subjects here dealt with are the 

 Copepoda, Tunicata, Ostracoda, Chajtognatha, 

 Amphipoda, Rotatoria, and Ceratium. With the vast 

 amount of material collected in course of the investi- 

 gations external records are incorporated in a dis- 

 cussion of the seasonal occurrence and distribution of 

 the species considered, and the hydrographic condi- 

 tions associated in each case with such. The annual 

 and seasonal distribution and intensity of many of the 

 more important species are shown in a number of 

 separate charts. From an economic point of view, 

 attention is directed to the importance of many of the 

 Copepoda and Amphipoda as constituting in a large 

 measure the food supply of Clupeoids, Gadid^, the 

 mackerel, and other marketable fishes. 



As bearing directly on questions of physical oceano- 

 graphy, Salpa and Doliolum among the Tunicata 

 afford important examples of warm-water species 

 drifted as annual visitors to our coasts by the agency 

 of the Gulf .Stream. Similarly, several species 

 of Ceratium show a distribution largely increased by 

 immigration through the Faroe-Shetland Channel into 

 the North and Norwegian Seas and beyond. Some 

 of the latter species have a second sphere of distribu- 

 tion in the West Atlantic, from Florida to Newfound- 

 land, and the author of this section, who has traced 

 some of them sparingly at wide intervals across the 

 .Atlantic to the American coast, is of opinion that the 

 two spheres of distribution are indeed in communica- 

 tion by virtue of the east-going oceanic movement. 

 Conversely, among the brackish-water Rotatoria, 

 species find their extension during the summer months 

 from the Gulfs of Finland and Bothnia over the Baltic 

 and outwards, mainly dependent on the periodic sur- 

 face outflow of low-salinity water in this region. For 

 the further elucilation of these complex problems, 

 more exact information is required concerning some 

 of the more critical species, and the need is felt, in 

 particular, for a greater extension of the area of 

 investigations to the westward and south-westward 

 of Ireland. 



