422 



NATURE 



[March i, 1^94 



physical properties which afford no evidence of being influenced 

 by molecular complexity. 



In the second are substances like the acids, water, and the 

 alcohols, for which the disturbing factor is, no doubt, molecular 

 complexity. 



The question of the generality of the results obtained is next 

 discussed. It is evident : 



(i) That over such temperature ranges as the observations 

 extend the results obtained at a particular value of the slope 

 may be regarded as general for all liquids, with the exception of 

 the alcohols, for which the relationships vary slightly as the 

 slope alters. A general expression connecting ihe viscosity 

 cu^fTicient with the slope is given. 



(2) It is further indicated, from comparisons made by the 

 use of slopes which varied from liquid to liquid, and which 

 were chosen according to definite systems, that in the present 

 state of the question equal slope is the most suitable condition 

 at which tu compare the viscosities of different liquids. 



With lespect to the relationships existing between the 

 magnitudes of the comparable temperatures of equal slope, it 

 appears : — 



(1) That these vary in a regular way with the chemical nature 

 of the subslances, except in the case of liquids like benzene and 

 propylene dibromide, giving viscosity curves which are abnormal 

 when compared with those of their homologues. 



(2) The temperature relationships may also be regarded as 

 general and thus independent of the value of the slope, except 

 in the case of the alcohols, which, in this respect, as in that of 

 viscosity at equal slope, are anomalous. 



The rest oi ihe memoir is concerned with the discussion of 

 certain general conclusions regarding physicochemical compari- 

 sons ; and it finally deals with other possible methods of obtain- 

 ing and comparing viscosity magnitudes. 



THE DYNAMICS OF THE ATMOSPHERE. 



TINDER this title a series of articles appeared in the 

 ^ Mete'orologische Zeitsclirift for May, August, and Septem- 

 ber, 1893, from the pen of Prof. M. Moller, of Brunswick, which 

 treat of many of the important processes that are at work in our 

 atmosphere. 



The principal feature in these discussions is that the author 

 treats the various phenomena as the result of complicated pro- 

 cesses, and inquires into their character separately, prior to at- 

 tempting to draw conclusions from them, so that some relations 

 are presented in anew form. 



With regard to ihe part which aqueous vapour plays in the 

 atmospheie, it is usually stated that the heat set free in conden- 

 sation during the formation of clouds greatly favours the origin 

 of ascending air-currents, but ^'uller lakes another view of the 

 matter. Two columns of air have usually been compared with 

 each other, having at their base similar initial temperature, but 

 in which ihe decrease of temperature with height proceeds in a 

 different manner, as one column is supposed to contain dry air, 

 that is very cold at the upper end, and the other moist air 

 warmed by condensation. But the author considers that this 

 difference of temperature does not actually occur in this 

 manner, and that all theories based upon this assumption 

 must lead to erroneous results. He states that as the air 

 of the upper strata has risen up previously, it has conse- 

 quently gone through the process of warming by con- 

 densation, so that the increase of heat caused by condensation 

 cannot produce by itself a higher temperature in the ascending 

 current than that possessed by the surrounding air, hence the 

 cause of the upward impulse, which has been attributed to the 

 aqueous vapour of the air, disappears. If it is wished to 

 produce a circulation of the air in two vertical tubes in com- 

 munication at both ends, the air in the bottom part of the 

 one tube must be warmed, while that in the upper part of 

 the other tube is cooled ; but if the source of heat is applied 

 at the top, a condition of stable equilibrium and rest takes 

 place. In the same v^ ay the condensation of the aqueous 

 vapour causes a warming of the upper strata of air, the 

 effect of which is generally to produce a condition of stable 

 equilibrium, contrary to the theory which assumes that the con- 

 densation of the vapour favours the ascending current, and 

 consequently gives rise to depressions. The author attri- 

 butes the chief cause of the origin of cyclones to horizontal 

 differences of temperature in the earth's atmosphere, to the 



steep gradients of the upper strata caused by them, and the 

 consequent strong movements of the air in those regions. He 

 agrees in the main with the views of Ferrel, but attributes 

 greater importance to the effect of friction against the rough 

 surface of the earth. The air which rises at the equator, and 

 moves in the upper regions towards the pole, takes, according to 

 the law of the preservation of the moments of rotation, 

 a west to east velocity, whose right-handed deflective force in 

 the northern hemisphere is opposed to the poleward motive 

 effect of the upper gradient. 



According to Prof. Moller, this right-handed force over the 

 dry zone, iu the belts of high pressure, on both sides of the 

 tropics, and in higher latitudes, becomes so great that a con- 

 dition of equilibrium of the forces is produced in the direction 

 of the meridians. Apart from local disturbances, the upper 

 wind here follows the parallels of latitude, unless owing to 

 friction, or the mixing of the upper and lower strata, a diminu- 

 tion of the upper current occurs, whereby the meridianal 

 deflecting force of the upper gradients gains the mastery over 

 the decreased right-handed deflective force arising from the 

 centrifugal effect. Only then, and in proportion as this 

 diminulii)n of the upper current occurs, does the upper 

 current follow the meridianal upper gradient. In this case 

 a part of the energy gained in the upper currents of the 

 atmosphere is transferred to the lower strata, so that there 

 the velocities which are directed from west to east increase. 

 The atmosphere, therefore, in the temperate and polar zones 

 is like a caloric machine, which first produces by meridianal 

 gradients of temperature the upper gradients of pressure, and 

 consequently an air current from west to east at a great height, 

 whose transference to the lower strata of air depends upon 

 opportunities of friction or .•nixture of masses of air. The meridi- 

 1 anal advance of air in the upper air-current is checked by the cen- 

 i trifugal force ; for the advance to the pole increases the velocity 

 of the west wind, and thus the centrifugal right-handed deflective 

 force whose effect stops the meridianal advance of air to the 

 pole. Moller states that this important relation of interchange 

 was not clearly expressed in Ferrel's theory. He first assumes 

 that a circulation between the hot and cold zones takes place 

 unhindered, and, provided the circulation takes place, he makes 

 the high velocities to exist in the upper current. Ferrel also 

 computes the great forces which would be necessary in order to 

 produce those high velocities, and he admits that these really 

 do not exist. He speaks of this theory as only approximately 

 correct, whereas the computed forces and great meridianal differ- 

 ences of pressure fail in nature, and the high westerly wind- 

 velocities, such as his theory requires, do not exist. 



Prof. Miiller concludes (l) that the regular and undisturbed 

 circulation of the atmosphere between the hot and cold zones 

 is not accomplished in the manner hitherto supposed, and as 

 has been presumed in Ferrel's calculations, and states that if 

 Ferrel's theory is to become of practical use, it will be necessary 

 to study more exactly the relations between the friction of air 

 on the surface of the earth, and especially the friction or the 

 mixture of air between upper and lower strata. (2) If friction 

 of air against the earth's surface is great, the velocity of the 

 winds is less ; but if friction, or mixture of air, between upper 

 and lower strata is great, then the lower winds blow more 

 violently. (3) In higher latitudes no storm can be caused by 

 horizontal meridianal gradients of temperature without mixture 

 or friction between the upper and lower strata. 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE. 



Oxford. — The Savilian Professor of Astronomy, Mr. H. H. 

 Turner, gave his inaugural address on Friday last, in the new 

 schools, before the Vice-Chancellor and a large audience. The 

 Professor illustrated his subject, "The International Photogra- 

 phic Chart of the Heavens," by numerous lantern-slides, and 

 referred particularly to the large share in the work allotted to 

 the Oxford Observatory, and to the progress which had already 

 been made. 



Prof. Sylvanus P. Thompson gave a lecture before the 

 Ashmolean Society on Monday last, on the subject of "Magic 

 Mirrors." The lecture was illustrated by numerous specimens 

 and experiments, and was much appreciated by a large audience. 



An election to the Sipthorpian Professorship of Rural 

 Economy is announced to take place in Easter Term, 1894. 



NO. 1270, VOL. 49J 



