45Q 



NA TURE 



[March 8, 1906 



ture, humidity, cloudiness, and wind. The trade wind, 

 limited to about iooo metres in thickness, varies in direc- 

 tion between north and east, is damp, and usually carries 

 cumulus or strato-cumulus clouds in its upper portion. 

 Above the surface trade is a current about 2000 metres in 

 depth, varying in direction between north-east and north- 

 west, but coming always from a direction to the left of 

 the lower wind when facing it. This current is extremely 

 dry and potentially warm, and its velocity is usually much 

 greater than that of the lower wind. At their plane of meet- 

 ing occurs a belt of calms or light winds with a marked 

 inversion of temperature, and this rise of temperature is 



1 PtRA TURE 

 Vertical Di< 



Lat 



relative humidity w 



of Temperature, Humiditv and Wind, 

 40 33' N., Long. 46 43' W. 



accompanied by a very decided fall of humidity, the re- 

 lative humidity in some cases falling to nearly zero. The 

 third stratum, which begins at a height of about 3000 

 metres, moves from a direction varying between east and 

 south or south-west, being generally from the east in 

 equatorial regions and from the south between latitudes 

 15° and 30° N. As observed on the Peak of Teneriffe, 

 this stratum was dry in its lower portion, but had a 

 slightly larger vapour contents than the air immediately 

 below. Alto-cumulus and alto-stratus clouds were seen 

 floating in it at a height of perhaps 4000 metres or 5000 

 metres, and from them light sprinkles of rain fell 

 occasionally. In passing into this upper current a rise 

 of temperature was noted, but this was less marked than 



Fig r.— Vertical Distribution of Temperature and Humidity, July 12, 

 1905 ; Lat. 27° 30' N., Lone. 16° 48' W. 



the rise encountered above the surface trade. Mr. Clayton 

 also deduces the following facts from the observations : — 

 (1) the Bases of the cumulus clouds are low over the 

 ocean, rarely exceeding 500 metres ; (2) the height of the 

 inverted temperature gradient varies from day to day 

 between 300 metres and 1500 metres, with a probable 

 average of 1000 metres, and its height also appears to 

 undergo a diurnal change, being lowest at night or in the 

 morning and highest in the afternoon ; (3) the adiabatic 

 rate of decrease of temperature prevails over the ocean at 

 night as well as during the day. 



The vertical distribution of temperature and humidity 



NO. 1897, V0L ' 73] 



revealed by our observations up to a height of 4000 metres 

 agrees in general with that found by Prof. Hergesell during 

 the cruises of the Prince of Monaco's yacht in 1904 and 

 1905 (see Comptes rendus de V Academic des Sciences, 

 January 30, 1905, and Bulletin du Musee Ocianographique 

 de Monaco, November 30, 1905). From the latter publi- 

 cation it is interesting to learn that a balloon, liberated 

 by Prof. Hergesell on August 7 last far to the westward 

 of the Canary Islands, indicated the same currents which 

 were found by us in the neighbourhood of these islands, 

 since it met the south-east and south-west winds above 

 the north-east trade. It is significant that this balloon 

 reached a greater height than did the 

 ~ac-„T other balloons, which showed winds 

 , having a northerly component. We 

 perceive that Prof. Hergesell no longer 

 denies the possibility of an upper anti- 

 trade in a lower latitude than the 

 ( lanaries, but now simply states that 

 in the central part of the Atlantic he 

 found almost exclusively north-west 

 winds, from which he concludes that 

 the route followed by the currents 

 bringing the air from the equator 

 appears to be less simple than had been 

 supposed, and seems to depend on the 

 relative positions of the continents and 

 1 N o oceans. The study of the daily isobars 



over the ocean, which was first made 

 under the direction of Le Verrier in 

 1S14, showed that the pressure is not 

 distributed in uniform belts, and that 

 the isobars are everywhere deflected by the influence of 

 temperature distribution dependent upon the land and sea, 

 relations which were demonstrated by M. Teisserenc de 

 Bort's study of isonormals more than twenty years ago. 

 Hence it would appear that' there are certain regions where 

 the anti-trade is more regular than elsewhere, the zone 

 between the Cape Verde and Canary Islands being no 

 doubt one of these ; but this view is quite contrary to 

 the idea that the south-east and south-west winds observed 

 in the upper atmosphere near these islands, and hitherto 

 accepted as proof of the anti-trade, are due to local in- 

 fluences, which Prof. Hergesell still affirms to be true. 

 A. L. Rotch. 

 I.. Teisserenc de Bort. 



THE TRANSFORMATIONS OF ROCK-MASSES.' 

 '"THE study of the changes which rock-masses undergo 

 under natural conditions is in itself by no means an 

 inconsiderable branch of geology, and its pervading import- 

 ance throughout the whole field of the science brings it 

 continually to the front in stratigraphical as well as peno- 

 logical research. The literature of the subject is a large 

 one, but until now no serious attempt has been made to 

 deal fully and comprehensively with the principles and 

 phenomena of metamorphism as a whole. Prof, van Hise's 

 wide experience in the Lake Superior region and elsewhere 

 has made him well fitted for a task to which he has devoted 

 seven years of labour ; and the outcome of that labour, as 

 represented in the massive volume before us, will have a 

 permanent value for all who come after him in this field. 



This treatise, as we are told in the preface, is " an 

 attempt to reduce the phenomena of metamorphism to order 

 under the principles of physics and chemistry, or, more 

 simply, under the laws of energy." Metamorphism is 

 understood to include all alterations of all rocks by all 

 processes. This extension of customary usage may be de- 

 fended on logical grounds, and it has the advantage of 

 constantly keeping in view the essential unitv underlying 

 the complex operations of nature ; but it involves a corre- 

 sponding enlargement of the subject-matter. The scrupu- 

 lous — almost relentless — manner in which the author follows 

 out in every detail the general scheme of treatment laid 

 down further swells the bulk of the volume, and, brought 

 out in the handsome style which characterises the produc- 



1 " A Treatise on Metannrphis 

 (Monoaraphs of the U.S. Geologii 

 13 plates. (Washington, T904.) 



By Charles Richard 

 urvey, vol. xlvii.) Pp. 



