2IO 



NATURE 



{Jan. i, 1880 



something which floats at a higher level than "pallio- 

 cirrus." Looking at one of the figures in which " cirro- 

 stratus" is portrayed, we recognise only cirrus, tend- 

 ing slightly to the form cirro-cumulus (Plate 3, Fig. 1). 

 Some of the other representations convey the idea of 

 clouds which would certainly be at a lower level than the 

 usual veil or bed of extensive sheet-cirrus. Some readers 

 may however be more fortunate than we have been in 

 recognising the form of cloud which the author intends to 

 designate as " cirro-stratus.'' His theory of the formation 

 of the varieties of clouds of the cirrus types is perhaps 

 as clearly expressed in the following as in any passage in 

 the book. " Void exactement ce qui se passe dans la 

 nature : lorsque les cirrus s'abaissent, ils se transforment 

 en cirro-stratus. Les aiguilles glacees de ce dernier nuage 

 infe'rieur sont plus compactes et abondantes, plus ddfinies 

 et mieux ge'ome'triquement distributes que les particules 

 moins abondantes et plus isoldes des cirrus supe"rieurs. 

 Ouand les cirro-stratus s'abaissent a leur tour, ils se 

 transforment en cirro-cumulus : la structure neigeuse 

 remplace la structure glacee par l'effet de la hausse de la 

 temperature. Les cirro-cumulus en s'abaissant eux-memes, 

 se transforment en pallio-cirrus ou en une couche neigeuse" 



(P- 29)- 



The compound "cumulo- stratus" Prof. Poey would 

 get rid of. We believe that Howard had himself a clear 

 idea of a distinct object when he employed this word ; 

 but up to the present time, owing to indistinctness of 

 verbal description, to ill luck as to illustrations, and to 

 other accidents, the word has had a desperately unfortunate 

 history, and Prof. Poey's objections to it consequently 

 come with great force. It is no exaggeration to say that 

 ■while we have seldom found two observers really agreed 

 as to the object denoted by this word, we have known the 

 word applied to every existing description of cloud, with 

 the sole exception of unmistakable cirrus. 



Poey's word " tracto-cirrus," the use of which he 

 advocates whenever the cirrus-clouds arrange themselves 

 in parallel bands, is an expressive term. But it is often 

 extremely difficult to decide whether the cirri are or are 

 not arranged in bands. And in treating the " tracto- 

 cirrus " as if it always occupied a iower level in the atmo- 

 sphere than cirrus, and the " pallio-cirrus " as floating 

 at a still lower level, the author appears to be straining 

 physical fact in order to strengthen the basis of his classi- 

 fication. There is, so far as we are aware, no evidence 

 to show that whenever cirrus adopts, as it does in a 

 majority of cases in most regions of the globe, the band 

 form, it sinks in the atmosphere, and that a further sub- 

 sidence takes place whenever it spreads itself into a veil or 

 sheet. 



The word "nimbus" is to share the fate of stratus 

 and cumulo-stratus. Here again we think the author 

 would have been more successful if he had preferred 

 reform to abolition. That two distinct beds of cloud, the 

 one at a high, and the other at a low level, frequently 

 exist when rain is falling, there is abundant evidence to 

 show, and perhaps this is especially the case during 

 extensive intra-tropical rains. But observers are at least 

 equally agreed as to the fact that a bed of cirrus may coexist 

 with a layer of low cloud, either with or without one or 

 more intermediate layers, without the occurrence of rain 

 or snow. And it is equally certain again that the majority 

 of passing showers are produced in a single mass of 

 cloud, not necessarily, and perhaps never, homogeneous 

 in structure in the portions near the earth and in those 

 which extend into the higher regions of the atmosphere, 

 but certainly not divided into two ocularly distinguishable 

 strata. These facts seem to be ignored by the author 

 when he substitutes " pallium " for " nimbus," and then 

 makes the rainy " pallium " to consist in all cases of 

 "pallio-cirrus" superimposed upon "pallio-cumulus." 



As regards the term " pallio-cumulus," we are again 

 obliged to hesitate in accepting it as a thoroughly descrip- 



tive title for a layer of low cloud, which has little in 

 common with cumulus except that it occupies much the 

 same level in the atmosphere. 



Another of the author's terms, "fracto-cumulus," which 

 he employs for those fragments of low cloud, which, though 

 not themselves hemispherical, are nascent or potential 

 cumuli, seems a useful word (perhaps only open to the 

 slight objection that the affix would be liable, if Poey's 

 system were adopted, to be confounded, especially in MS. 

 reports, with his other affix tracto). His French equiva- 

 lent " nuage venteux"is, however, not sufficiently com- 

 prehensive,and is open to the same objection as the English 

 word " scud," which involves the idea of rapid motion. 

 The low cloud-fragments are not necessarily either the 

 concomitants or the precursors of wind. 



A highly interesting section is devoted to the clouds 

 which have been in England denominated "pocky clouds." 

 The fact that this name has been applied to several distinct 

 varieties of clouds is certainly not unduly pressed by 

 the author ; in truth he scarcely appears adequately to 

 realize the amount of misapprehension which has existed 

 on the subject of these clouds. A Latin affix would 

 certainly have the desirable effect of obliging the observer 

 to give attention to the generic form of cloud from which 

 hang the characteristic bladder-like protuberances ; thus 

 clouds of the cirrus and of the cumulus type, presenting 

 this peculiarity, would no longer be registered under a 

 single title. But Poey's proposed affix "globo " does not 

 appear satisfactory, for there is reason to suspect that 

 some observers would be likely to apply it to any spherical 

 or apparently spherical masses of cloud. How easily, in 

 cloud terminology, misapprehension arises from the mere 

 sound of a name the author himself in this very section 

 illustrates, when he mistakes the " roll-cumulus " of the 

 English Meteorological Office for ill-developed pocky 

 cloud. 



Beset with difficulty as all questions of cloud classifica- 

 tion must necessarily be, we yet believe that at the present 

 time, and for the present, a' useful and unobjectionable 

 compromise might be made between the systems of 

 Howard and of Poey. 



Stratus might, without dissolution, leave the surface 

 of the earth, as it already has done in numerous meteoro- 

 logical records, and be applied to all clouds, not of the 

 cirrus type, which arrange themselves in a horizontal 

 bed. Cirro-stratus would then form the descriptive title 

 of the ice-clouds of the higher regions whenever these arc- 

 disposed m a bed, sheet, or veil. The terms cumulus 

 ami cirro-cumulus may remain undisturbed. If the title 

 cumulo-stratus have not received mortal injury from 

 abuse, it might be applied to those peculiar descriptions 

 of "mackerel cloud" or "nuage pommele"," which are 

 only at a moderate elevation, and are not in physical 

 structure cirro-cumuli, a class of clouds which much need 

 a distinctive title. If nimbus is to be retained, it might 

 be subdivided into its two essentially distinct varieties, 

 the massive local shower-cloud, and the extensive bank of 

 composite rain-cloud ; and for these varieties the titles 

 cumulo-nimbus and strato-nimbus, or some equivalent 

 expressions, might come into use. The expressive 

 fracto-cumulus should have its place secured ; and this 

 affix of Poey's may have further applications ; detached 

 pieces of those clouds which tend to arrange themselves 

 in horizontal beds (pieces which are in no sense the nuclei 

 of cumulus clouds), may conveniently be termed fracto- 

 stralus, while to the little wavy or broken shreds of ice- 

 cloud which Poey seems to designate "cirro-strati," the term 

 fracto-cirrus might perhaps be applied. For the bizarre 

 ""pocky clouds," which, though not nearly so rare as is 

 usually suposed, are certainly not common, an affix, if 

 descriptive, would be none the worse for being somewhat 

 outlandish, and possibly " mammato" or even "papillate.," 

 might be acceptable. If the course suggested in the 

 present article be adopted, no very serious changes will 



