132 



NATURE 



{Dec. 8, 1887 



— cirrus, cumulus, stratus, nimbus and cumulo-nimbus, 

 cirro-cumulus and cumulo-cirrus, cirro-stratus and strato- 

 cirrus, together with strato-cumulus— comprise all the im- 

 portant kinds of clouds ; and there are really only five 

 distinct types of structure — cirrus, stratus, cumulus, nim- 

 bus, and cirro-cumulus. Prof. Hildebrandsson and myself 

 consider that the ten words above mentioned, com- 

 pounded out of only four Latin words, are practically 

 sufficient for all ordinary purposes. 



Specialists in clouds will of course want more minute 

 varieties, such as different names for some of the kinds 

 of cirrus, and for the low broken clouds, such as scud, 

 wrack, &c. There are also a whole class of pendulous 

 clouds, such as festooned stratus, pocky cloud, or mam- 

 mato-cumulus ; and the long black wreaths of cloud in 

 front of certain types of thunderstorm, but these are all 

 very local, and also very short-lived, so that they need 

 only be mentioned here. 



So far for the mere external forms of clouds as they 

 would strike a savage or an artist ; but to the meteorologist 

 there is a philosophy behind them. In England some 

 forms presage wind and rain, others indicate the advent 

 of fine weather ; while recently it has been shown that 

 different kinds of clouds are developed in different paits 

 of cyclones and anticyclones. For instance, cirro- 

 stratus forms in front, cumulus in rear, of a cyclone ; 

 while fleecy cirro-cumulus is very characteristic of the 

 western side of the anticyclones. 



But then we are met by the apparent paradox that 

 precisely the same forms of cloud are found on the 

 equator where neither cyclone nor anticyclone was ever 

 developed. Moreover, the same cloud does not prognos- 

 ticate the same weather all over tlie world, and even in 

 the same country the same cloud may indicate either good 

 or bad weather according to the circumstances under which 

 it is developed. For instance, cumulus in England is 

 sometimes the associate of a fine day, other times the 

 forerunner of a shower. 



The clue to the whole puzzle lies in the fact that the 

 same form of cloud can be produced under totally differ- 

 ent circumstances. Vapour-laden air can only condense 

 into cloud, and then be drawn out or rolled about between 

 different currents in a very limited number of ways, and 

 hence the small number of really distinct varieties of 

 cloud structure. 



Let us take the case of cumulus in detail as an example 

 of general principles. Cumulus is always the condensed 

 capital of an ascensional column of air, but the source of 

 the uptake need not always be the same. For instance, 

 air may rise either (i) from ordinary evaporation on a 

 fine day ; (2) from the uptake of a cyclonic vortex ; (3) 

 from the collision between two opposite currents. 



The first — evaporation — is the source of fine-weather 

 cumulus in England and all over the world ; while the 

 uptake of a cyclone is the cause of rainy cumulus wherever 

 such eddies are formed. The rainy cumulus of the 

 equator is the product of squalls and thunderstorms 

 whose nature at present is unknown in most cases ; but 

 one very common cause is the collision between the land 

 and sea breezes of the tropics. The two opposing cur- 

 rents meet, one is forced upwards, and then mountainous 

 cumulus is the result. The cumulo-nimbus in Fig. 3 is 

 over a thunderstorm in Borneo, due to the collision of the 

 land and sea breezes. 



All, therefore, that we can say for certain when we see a 

 cumulus cloud is that an ascensional current of air has 

 risen to the level of condensation. What future weather 

 the cloud prognosticates depends on circumstances, and 

 must be judged by our experience and knowledge of the 

 climate in which we may happen to be. Clouds always 

 tell a true story, but one which is hard to read ; and the 

 language of England is not the language of Borneo. 

 The form alone only shows that a certain form of condens- 



'J 



ation is taking place ; the true import must be judge 

 by the surroundings, just as the sense of many words can 

 only be judged by the context. 



Ralph Abercromby. 



FIFTH ANNUAL REPORT OF THE FISHERY 

 BOARD FOR SCOTLAND. 



THE Report for 1886 contains so much of general 

 interest that it deserves the attention of many who 

 look upon a Blue-book as the driest of reading, only 

 attractive to those whom it may immediately concern. It 

 is desirable that the scope and practical aims of the 

 Board should be more generally known, and the public 

 should appreciate the excellent work done by it, instead 

 of regarding this as the mere outcome of scientific lean- 

 ings to certain lines of investigation. The fisheries of 

 Scotland continue to be very productive, and nothing is 

 more striking about them than the great and increasing 

 yield of the herring fishery. Though this increase and 

 the low price at which the herrings have been sold have 

 proved a great boon to the community, especially to the 

 poorer classes, it is deeply to be regretted that the crews 

 sustained very heavy losses from the glutting of the 

 market consequent on the large takes and low prices. A 

 striking feature of the summer herring fishery of 1885 was 

 that many in-shore grounds where herrings had been 

 found in great abundance in previous years but which had 

 been recently all but deserted were restored to their former 

 fertility. This was even more marked in the season of 

 1886, as all along the east coast from Montrose to the 

 Pentland Firth there seemed to be one immense un- 

 broken shoal of herrings, lying from one to ten miles off 

 land. At no former period in the history of this fishery 

 were the catches so heavy. The winter herring fishery 

 on the east coast was the most productive ever known, 

 yielding a total catch of 128,441 crans. The gross total 

 value of the sea and salmon fisheries of Scotland for 1886 

 was ^2,550,778 8j. id. 



During the past year the scientific work consisted 

 chiefly in carrying on the trawling experiments required 

 by the recent Act of Parliament (Sea Fisheries (Scotland) 

 Amendment Act, 1885), but in addition investigations 

 were made as to the development, artificial hatching, 

 structure, and habits of the more important useful fishes. 

 An important part of the inquiry as to the influence of 

 trawling consisted in arranging to obtain statistics show- 

 ing the quantities of fish landed from the restricted 

 areas, and the conditions under which they were cap- 

 tured — an extremely difficult matter to arrange. 



The Board's marine station at St. Andrews has again 

 been under the direction of Prof. Mcintosh, whose Report 

 shows that important work on the life-histories and de- 

 velopment of the food-fishes has been done at this station 

 by him and Mr. E. E. Prince, by Dr. Scharff on the 

 intra-ovarian eggs of food-fishes, and by Mr. Wilson 

 on the development of the common mussel. The 

 memoir first mentioned, viz. that on the development and 

 life-histories of the food-fishes, is now ready for publica- 

 tion, and is illustrated by thirty-one quarto plates. Its 

 size and the nature of the illustrations of course render it 

 unsuitable for a Parliamentary Blue-book. 



The " Report on the Trawling Experiments on the 

 East Coast, Part I. Preliminary," by Prof Ewart and 

 Sir J. Ramsay Gibson-Maitland, gives the results of an 

 important item in last year's work. The Act already 

 referred to having empowered the Scotch Fishery Board 

 to frame by-laws for the better regulation of sea-fishing, 

 and one such law having been framed, passed, and con- 

 firmed, it was necessary to make arrangements to dis- 

 cover, if possible, what influence the prohibition of 

 trawling under the by-law would have in leading to 



