December i6, 19 15] 



NATURE 



441 



loint of picric acid (122°) than that of trinitrotoluene 

 S2°) is another disadvantage, but this may be over- 

 ome by the use of certain eutectic mixtures. One 

 -Lich contains forty parts of picric acid with sixty 

 Marts of trinitrometacresol (cresylite). The mixture 

 nelts at 85°, and, after solidification, on reheating 

 (ocomes plastic at 70°, which permits of compression 

 <j high density in the shell. 



The various smokeless powders are dealt with, 

 \ieille's work in the development of pure nitrocellu- 

 lose powders receiving special mention. It is pointed 

 out that, in addition to control of the rate of burn- 

 ing by variation in the form and size of the pieces, a 

 greater proportion of the more slowly burning 

 soluble" nitrocellulose affords a means of control; 

 ihus for small arms the "soluble " may be 25 per cent., 

 for large marine guns 50 per cent., the remainder 

 being "insoluble" nitrocellulose. 



Nobel's invention of the use of nitroglycerine as a 

 non-volatile solvent is referred to as a great improve- 

 ment, there being many disadvantages in the use of 

 volatile solvents. A more recent non-volatile 

 ;elatiniser is dinitrotoluol, the Italian Avigliani 

 powder being composed of "soluble" nitrocellulose 

 fifty parts, "insoluble" N.C. twenty-five parts, 

 dinitrotoluene twenty-five parts. 



The use of stabilisers is next considered. It is 

 hown that nitrocelluloses, like other nitric ethers, 

 ire liable to slow h3'drolysis, with the formation of 

 oxides and acids of nitrogen, these actions being 

 promoted by moisture and rise of temperature, the 

 rate being greatly increased by the catalytic action of 

 the products. These actions lead to irregular 

 ballistics, and even to spontaneous ignition. 

 Stabilisers, of which diphcnylamine is the most 

 ;<'nerally used (in ballistitc, BN powder, etc.), 

 absorb the liberated nitrogen compounds and pre- 

 vent, or at least greatly retard, the decomposition. 



In conclusion, particulars are given of the cele- 

 brated 75 mm. French gun. The projectile weighs 

 72 kilos., and has a muzzle velocity of 520 metres 

 per second. The charge of powder B, in flake form, 

 is 720 grams. It is shown that the gun, as a heat 

 engine, gives an efficiency of 3;! per cent. To an 

 increase in this efficiency the author looks for further 

 progress in the future. 



THE MINUTE LIFE OF THE SEA A 

 T^HE quantitative examination of the microplankton 

 -*- of the North European waters is the sub- 

 ject of the present important memoir, which 

 is the outcome of a resolution of the International 

 Council to take advantage of cruises in Denmark, 

 England, Holland, Norway, and Sweden in the spring 

 of iqi2 for the collection of plankton samples taken 

 liy means of the water-bottle at depths ranging from 

 o to 100 metres and more. In this way a series of 

 accurately determined species is followed from sample 

 to sample, and the distribution of these species is 

 used to illustrate the laws of production and destruc- 

 tion of organic substance in the ocean. Prof. Gran 

 has exhaustively examined the whole of the material 

 collected with the exception of the greater part of 

 the Scottish collections, for which Miss Ogilvie is 

 responsible ; a special chapter being devoted to this 

 portion of the work. The samples were all preserved 

 bj' adding Flemmincr's solution to the water directly 

 it was collected. This method, although admittedly 



1 H H. Gran J "The Plankton Production in the North European Water 

 in the Soring of 1012." Conseil Permanent Intenational pour I'explora'ions 

 <le la Mer. BuUetin Planktonique pour I'annes 1912 (continuat'on du 

 liulletin Trittiestriel des rtfsultats acquis pendant le« croisieresp^riodioueset 

 dans les p^rioHes int'rm<5 fnres, P .rt'e D). Public par le Bureau du Conseil 

 avec I'assist.ince de C. H. 0«tenfe1d. <-v.-,-^(^ Ju service planktoniquf. 



restricted, answers well for the preservation of all 

 important Plankton species, as is shown by the fact 

 that, when comparing the living material from 

 Fl0(leveigen, Skager Rak, with the preserved, no 

 species were found which were not present in the 

 preserved material. For examination, Lohmann's 

 centrifugal method is used, and the number of organ- 

 isms (cells) per litre given in a series of tables with 

 hydrographical data. Even delicate Peridiniales such 

 as Gymnodinium, and Infusoria, especially Labcea, 

 are well preserved, and are shown to form an im- 

 portant part in the economy of the sea. 



Part i. gives a descriptive account of the plankton 

 from each area taken separately. Of these the Danish 

 results from the Skager Rak, taken both in February 

 and in June, are of special interest. The colder sur- 

 face water of the Skager Rak in February is found 

 to contain an exceedingly rich Diatom plankton, 

 which the author attributes not to the low tempera- 

 ture, but probably to the fact that the surface water 

 is specially rich in some nutritive substance necessary 

 to the development of the Diatoms. In June, this rich 

 surface Diatom plankton has almost entirely dis- 

 appeared, different species of Ceratium taking their 

 place. The Danish water investigations also bring 

 out striking results with regard to the relations ex- 

 isting between the assimilating algae and oxygen 

 tension in the different layers. 



In Part ii. new light is thrown upon the distribution 

 and biology of the separate species. Nitzschia deli- 

 catissima, Cleve, is found to be the commonest of all 

 species in the plankton from the ocean round the 

 Shetlands and the Faroes, having in places the large 

 density of more than a million cells per litre. With 

 regard especially to the Ceratium species, it is shown 

 that passive sinking of the cells plays an important 

 part in their vertical distribution, and this statement 

 applies also to many of the other genera. The species 

 of Laboea are true surface forms and are very 

 abundant : " The whole of the ocean round Scotland 

 and the Faroes contains, at the ' surface, on an 

 average, ore for each cubic centimetre of sea-water." 



In the extensive discussion on general conditions of 

 life and of plankton production, taking the many 

 factors into account, the conclusion is arrived at that 

 with the assimilating algae the optimum production 

 is near the surface, although the maximum at certain 

 periods may be at a greater depth. Thus, in the case 

 of the Ceratium species, although in the present in- 

 vestigations the greater number were found to occur 

 at depths between 15-20 metres, it does not follow 

 that this represents the depths of optimum production*. 

 In fact, other researches show it to be generally nearer 

 the surface. The author suggests that by far the 

 greater number of the assimilating plankton algae have 

 their maxima close to the surface, probably not as 

 deep as 10 metres. 



The last portion of the work on the horizontal 

 quantitative variations of the plankton shows the 

 influence of the coastal waters on distribution. The 

 entirely different conditions of the area round Scotland 

 and the Faroes compared with the Skager Rak and 

 the north-eastern corner of the North Sea is thus 

 explained bv- their supply on the one hand from 

 Scotland and the Faroes, and on the other through 

 the Baltic current from the Scandinavian coastal sea. 

 Throughout the investigation runs the same idea 

 binding the whole together and emphasising the im- 

 portance of a permanent supply of nutritive substance 

 from land. This nutritive substance taken up by the 

 sea forms the means of subsistence of all plankton 

 organisms which, orierinating from the coastal waters, 

 spread out from thence into the more distant waters 

 of the ocean. M. V. l- 



NO. 2407, VOL. 96] 



