July 



1922] 



NA TURE 



91 



years ago by Prof. G. A. J. Cole. There can be little 

 doubt that Rockall is the last remnant of a former 

 extensive land surface. 



The Geological Mapping of the Globe. — In 

 these columns attention has been directed from time 

 to time to the maps issued in connexion with regional 

 memoirs, such as -those on Australian states, Sinai, 

 and Mesopotamia. We may now add Lange Koch's 

 geological map of Palaeozoic strata in north-west 

 Greenland, 1 : 2,000,000, attached to his paper on 

 " The Stratigraphy of North-west Greenland " (Med- 

 delelser fvo Dansk. geol. Foi-en., vol. v., No. 17, 1920 — 

 foreword dated May 1921). In this memoir the 

 earlier Pakeozoic systems are shown to have been 

 involved in the Caledonian folding, which is thus for 

 the first time traced across the Atlantic interval 

 R. C. Wilson, in " The Geology of the Western Rail- 

 way " (Geol. Surv. Nigeria, Bull. 2, 1922, price 

 1 ys in/.), includes a coloured map of country north 

 1 i agos, scale 1 : 250,000, and records Eocene beds 

 near the coast, followed by areas in which composite 

 gneiss is prominent. An immense amount of informa- 

 tion as to geological knowledge of the countries 

 bordering the Pacific has been brought together in 

 the Proceedings of the First Pan-Pacific Conference, 

 part 3, published at the office of the Honolulu Star 

 Bulletin, 1921. M. Emm. de Margerie [Annates de 

 Geographie, vol. xxxi., p. 109, 1922), in criticising, 

 with a query, " Une nouvelle carte geologique du 

 monde ? " points out that the production of such a 

 map is beyond the powers of any one geologist. 

 While indicating defects in a recent publication, he 

 provides valuable notes on material not yet utilised. 

 Hence his essay usefully records a number of publica- 

 tions on regions recently explored. 



('.laze Storm in America. — The great glaze 

 3i 1111 oi February 21-23 m the Upper Lake region of 

 the United States of America is discussed by Prof. 

 A. J. Henry and Messrs. J. E. Lockwood and D. A. 

 Seele} oi the U S. Weather Bureau, and is published 

 in the U.S. Monthly Weather Review for February. 

 A large amount of damage was done to overhead 

 telegraph, telephone, and other transmission lines 

 in the upper Mississippi Valley and in the States of 

 Wisconsin and Michigan. A serious loss was sus- 

 tained by shade and ornamental trees and orchards, 

 a loss which cannot be replaced within the lifetime 

 present generation. The storm, in common 

 with others of a similar nature, had a cold surface air 

 current which was overrun by a warmer current, 

 the rain which was condensed in the upper current 

 falling upon objects having a temperature some degrees 

 below s- I', was frozen as it reached them. The dia- 

 meter of the ice-covered wires varied from a few tenths 

 of an inch to 2-5 in. or more, forming a rod of ice as 

 thick as a man's wrist, and added to this was the weight 

 of icicles which formed along the wires, often very close 

 together, and varying in length from 3 to 12 inches. 

 Often 2 or 3 miles of telephone wires went down at one 

 time. At Oshkosh a small piece of ice-covered branch 

 weighed 2 pounds; without the ice it weighed 2 

 ounces. In Michigan the ice, sleet, and snowstorm 

 was one of the heaviest on record. Millions of dollars 

 worth of properly was destroyed. In many orchards, 

 2 5"75 P er cent, of the older trees were broken off 

 entirely. At Arcadia a short twig weighing 1 ounce 

 had an ice coating of 2 pounds. Several observers 

 reported the ice coating to weigh 20 to 40 times as 

 much as the supporting branch or wire. 



New Theory of Cyclones. — During the last 

 twenty years our knowledge of the actual movement 

 of the air in a cyclone has increased materially 



NO. 2750, VOL I io] 



and it lias become more and more difficult to reconcile 

 it with the theory of cyclone formation advanced by 

 Ferrel 60 years ago. It is only recently that tht 

 work of meteorologists in this country and abroad 

 has led to a more satisfactory theory, which has 

 been given a precise form by V. Bjerknes and his 

 son J. Bjerknes, in a series of papers dating from 

 191 7 to 1921. A thoroughly readable account o'i 

 the present state of the theory will be found in an 

 article by Dr. E. Kuhlbrodt in the issue of Die 

 Wiss.enscha.jteu for May 26. According to Dr. 

 Kuhlbrodt the north polar regions are covered by 

 a cap of cold air which thins out as it extends down- 

 wards into temperate latitudes and ends in general 

 about latitude 40 , but may disappear at latitude 

 50 over a few degrees of longitude. Above the 

 cold cap is a considerable thickness of warm air 

 derived from the south and having a motion to the 

 east. Where the surface of separation of warm and 

 cold air comes down to the earth's surface .il .111 

 unusually high latitude a cyclone is produced, which 

 is 1 arried to the east by the movement of the warm air. 

 The distribution of wind and weather to be expected 

 in such a region is shown to be in agreement with 

 observation. 



Weather at Blue Hill, U.S. — Meteorological 

 observations made at the Blue Hill Observatory, 

 under the direction of Prof. Alexander McAdie, during 

 102 1. .ire published in the Annals of the Astronomical 

 Observatory of Harvard College. The observational 

 data complete an unbroken period of thirty-six 

 years, 1886-1921, and include pressure, temperature, 

 wind direction and velocity, humidity, sunshine, 

 cloudiness, and precipitation. It is estimated that 

 the series should extend over at least fifty years for 

 tiir establishment of proper normals. A table is 

 given showing advance of the seasons for thirty-six 

 years, 1886-1021. It is interesting to note that the 

 earliest autumn frost for the whole period occurred 

 on August 21 in [908, and 111 tin-, year the first snow- 

 fall in autumn occurred on December 7, which is the 

 latest of the whole period, an anomaly which would 

 scarcely be expected. The rainfall table giving the 

 monthly amounts for the several years shows a large 

 and varying range of measurement in all months. 

 The average annual rainfall is 46-59 in., ranging from 

 4-7 in. for March to 3-20 in. for June. 



A Differential Refractometer. — Messrs. Bell- 

 ingham and Stanley, Ltd., has constructed a 

 differential refractometer for measuring very small 

 differences between the refractive index of two 

 liquids. The design of the instrument is based on 

 the method described by Hallwachs. The liquids 

 are contained in a glass cell and are separated bv a 

 thin glass plate. Light from the source is admitted 

 to the liquid of lower refractive index at grazing in- 

 cidence on the separating glass plate, which it traverses 

 and then passes through the second liquid at a 

 small angle to the glass plate, the magnitude of this 

 angle depending on the difference between the 

 refractive indices of the two liquids. By means of 

 an observation telescope the axis of which is ap- 

 proximately in the plane of the separating glass 

 plate, the limiting position of the emergent ra\ from 

 the cell can be observed and the position measured 

 by the screw motion which rotates the cell with its 

 supporting table. In the case of liquids ha ing 

 indices approximating to that of water a difference 

 in index of 000001 corresponds to an angle of emerg- 

 ence of about \ of a degree. The instrument can 

 thus be made extremely sensitive, and is partu ularh 

 valuable for the detection of small quantities of 

 impurities in liquids. 



