164 



NA TURE 



[June 18, 1896 



In the rubbi-'i-gallieiint; industry, which is at once theweaUh 

 and bane of this part of tlie world, the implements in use are 

 of the most primitive kind, but the average earnings can easily 

 De three pounds per day during the dry season, and the facility 

 of earning so much money with little exertion makes the in- 

 habitants unwilling to engage in more arduous labour. 



A narrow path leads from the hut on the water's edge into the 

 forest from one rubber-tree to another, the path eventually 

 returning to the hut. The trees are cut on the morning round, 

 and the rubber is gathered in the afternoon. As soon as it 

 arrives at the hut a fire of oily palm-nuts (Altaica excelsa) is 

 lighted, and the thin sap thickened in the smoke For this 

 purjiose a paddle is used, on to which the .sap is poured with a 

 small earthenware or tin vessel. The smoke soon thickens it, 

 and a new layer is poured on until the well-known flat cakes of 

 india-rubber have been formed. 



Owing to the rise of the river during the rainy season most of 

 the huts have to be abandoned, and it can easily be imagined how 

 comfortless they are. Nearly all of them are built on piles, and 

 most of them are thatched with palm-leaves. There is hardly 

 any attempt made to cultivate the .soil, such as it is, but every- 

 thing is imported. The s.s. Cainelense, in which the surveying 

 parly went out, was laden with cabbages, onions, and potatoes, 

 part of which went as far as Iquitos in Peru. 



Chiefly owing to this want of provisions, and to the generally 

 careless mode of life, the mortality among india-rubber gatherers 

 is very great. 



Everything Bates and Wallace have said of this region remains 

 as true as it was forty years ago, and hardly anything new can 

 be added to their de.scription of the general features of the 

 Amazon valley ; but the town of Manaos has completely changed 

 its character since it was made the capital of that region in 

 1853. '^ town quite European in its features has arisen in the 

 midst of the forest, and to the benefits of rapid transport, to which 

 it has owed so much, there is now added the characteristic lever 

 ■of modern progress, the annihilator of space and time — electrical 

 .communication. 



NOTES ON CLOUDS} 

 "T^HERE are two points connected with clouds on which I wish 

 to make a few remarks. The first is on the classification 

 ■of clouds, and the second on the manner in which certain forms 

 of clouds are produced. It may be as well to remark at the out- 

 set that the observations are those of an "outsider," being 

 in a department of meteorology to which I have given but 

 little attention, and they have been written with a view of call- 

 ing the attention of specialists, and getting their opinion on the 

 subject. 



It appears to me that in classifj'ing clouds they ought first of 

 all to be divided into two great classes. In the one class should 

 be placed all clouds in the process of formation, and in the 

 other those in the process of decay. The two classes might be 

 called Clouds in Formation and Clouds in Decay. We may 

 take Cumulus clouds as an example of the former, and Nimbus 

 of the latter. My observations made on the clouds themselves 

 have shown that there is a difference in the structure of these two 

 classes of clouds. In clouds in formation the water particles are 

 much smaller and far more numerous than in clouds in decay ; 

 and while the particles in clouds in decay are large enough to be 

 seen with the unaided eye when they fall on a properly lighted 

 micrometer, they are so small in clouds in formation that, if the 

 condensation is taking place rapidly, the particles cannot be seen 

 without the aid of a lens of considerable magnifying power. In 

 the former case the number of particles falling per square milli- 

 metre is small, while in the latter they are so numerous that it is 

 impossible to count them. 



It appears that one good end might be served by adopting this 

 classification. It would direct the attention of observers more to 

 looking on the processes going on in decay for an explanation of 

 many of the forms observed in clouds. In most books on clouds, 

 when describing the different shapes of clouds, it is almost 

 always assumed that they are in process o{ formation., and the 

 whole explanation of the shapes taken liy the clouds is founded 

 on this supposition. Now, it is very evident that very many 

 clouds are in the process of decay, and their forms can only be 

 explained by the processes going on under these conditions. 



This brings me to the second point in this communication, 



' P.iper read by John Ailkeii, F.R.S., to the Roy. Soc. of Edin. on 

 May 4. 



NO. 1390, vor.. 54] 



namely, the manner in which ripple-marked cirrus clouds are 

 produced. The explanation which has generally been accepted 

 of the formation of this form of cloud is, that the ripple mark- 

 ings are due to the general movements of the air giving rise to a 

 series of eddies, the axes of the eddies being horizontal, and 

 roughly parallel to each other. It is very evident that the air 

 revolving round these horizontal axes, that is, in a vertical 

 plane, will at the lower part of its path be subjected to com- 

 pression, and at the upper part to expansion. The result of this 

 vvill evidently be, supposing the air to be nearly saturated with 

 moisture, a tendency for cloudy condensation to take place in the 

 air at the upper part of its path, and it is this cloudy condensation 

 in the upper part of the eddies that is supposed to produce the 

 ripple-like cirrus ; each ripple mark indicating the upper part of 

 an eddy. One objection I have always felt to this explanation 

 is, that it is difiicult to imagine that the small amount of eleva- 

 tion and consequent expansion and cooling could give rise to so 

 den.se an amount of clouding as is generally observed. Any 

 clouding produced in this way one would expect to be extremely 

 thin and filmy. I have for the last few years made frequent 

 observations of these clouds, and I have to admit I have never 

 once seen them in the process of formation, or seen one appear 

 in a clear sky. In all cases that have come under my observa- 

 tion, these ripple clouds have been clouds in decay. They are 

 generally formed out of some strato-cirrusor similar cloud. When 

 we observe these strato-cirrus clouds in fine weather, it will be 

 found that they frequently change to ripple-marked cirrus clouds 

 before vanishing. The process of their forination would seem 

 to be : the strato-cirrus gradually thins away till it attains such a 

 depth, that if there are any eddies at its level, the eddies break 

 the stratus cloud up into parallel or nearly parallel masses, the 

 clear air being drawn in between the eddies. It will be observed 

 that this explanation requires the eddies, but not to produce the 

 clouding, only to explain the breaking up of the uniform cirrus 

 cloud into ripple cirrus. 



One thing which supports this explanation is, that lenticular- 

 cirrus clouds are frequently observed with ripple markings on 

 one or more sides of them just where the cloud is thin enough to 

 be broken through by the eddies. If we watch these lenticular- 

 formed clouds under these conditions, we frequently see the 

 ripple markings getting nearer and nearer the centre as the 

 cloud decays ; and at last, when nearly dissolved, the ripple 

 markings will be seen extending quite across the cloud. It seems 

 probable that " mackerel " and other cloud forms may be 

 produced in the same way. 



The shapes which these ripple cirrus clouds assume are much 

 more varied than is generally supposed. I lately observed a 

 most interesting form in the south of France while the mistral 

 was blowing strongly. There were a feiv cirrus clouds in the 

 sky at the time, and one of these was rapidly being broken up 

 into irregular ripple forms, but at one point there was formed a 

 most perfectly cylindrical-shaped piece, its length being about 

 twenty times its diameter. The whirling effect of the eddy 

 was very evident by the circular streaking of the clouding. 

 P'urther, this cloud was evidently hollow, that is, the interior 

 was filled with clear air as the cloud was thinnest along the axis, 

 and it had all the appearance of a revolving tube of cloudy air. 



It is not contended here that ripple clouds are never produced 

 in the manner which has generally been accepted, only that so 

 far as my observations go they have never been observed 

 forming in the manner supposed. It is hoped that others will 

 put the explanation here offered to the test of observation, and 

 it is principally with a view of getting others to repeat the 

 observations that this has been written. 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE. 



Cambriiice. — In the Mathematical Tripos List published on 

 June 16, Mr. W. G. Fraser, of (Queens', is Senior Wrangler, 

 Messrs. Barnes, Carson, and Wilkinson, all of Trinity, are 

 bracketed for the second place, and four members of St. John's, 

 Messrs. Edwardes, Houston, Cook, and Turner, follow in two 

 brackets, fifth and seventh. Miss Longbottom, of Girton, has 

 the twelfth place. 



In Part II. seven names appear in the first division of the first 

 cla.ss, beginning with Mr. Bromwich, of St. John's, the Senior 

 Wrangler of last year. 



Mr. A. C. Dixon, of Trinity College, has been approved for 

 the degree of Doctor of Science, in consideration of his mathe- 



