April 27, 18 76 J 



NA TURE 



21 



four classes : — i. Those which occur when the isobar, 

 passing through St. Petersburg, bounds a space of low 

 pressure, or when St. Petersburg is included within the 

 area of a cyclone ; 2. When the isobar bounds the space 

 of high pressure, or is within the area of an anticyclone ; 



3. When it is in the calm centre of an anticyclone ; and 



4. When the isobar does not, at least on the map of 

 Europe, inclose a space, but stretches away in a line 

 which is either straight or irregularly waved. This divi- 

 sion is carried out as regards the two great divisions of 

 the year, viz., the cold half, extending from October to 

 March, and the warm half from April to September. 



The following will indicate the importance of the results 

 arrived at : — i. Duriuj^ the cold half of the year, northerly 

 winds (N.E. and N.) when connected with a cyclone have 

 the pressure o"37o inch below the average, the tempera- 

 ture a'^ above the average, the relative humidity 90, and 

 the sky all but completely covered with cloud ; with an 

 anticyclone, pressure is 02 71 inch above the average, 

 temperature 8^"6 below the average, humidity 84, and sky 

 only three-fourths covered ; and with a straight indeter- 

 minate isobar, pressure is o"20t inch above the average, 

 temperature ^"'^ below the average, humidity 89, and sky 

 less than three-fourths covered. 2. During the warm 

 half of the year, norlhtrXy winds connected with a cyclone 

 have pressure o'i92 inch, and temperature 5^"4 below the 

 average, humidity 87, and cloud 8 ; with an anticylone 

 pressure is 0*206 inch, and temperature o"'5 above the 

 average, humidity 75, and cloud 4 ; and with straight 

 indeterminate isobars, pressure is 01 04 inch above, and 

 temperature 3''4 below the average, humidity 76, and 

 cloud 5. 



As regards the S.E. wind, with a cyclone the tempera- 

 ture is 7'''2 above the average in winter, but only i^'8 in 

 summer ; and with an anticyclone, 4^0 below the average 

 in winter, but 2''"5 above it in summer. Again, with 

 straight isobars, S.E., S., and S.W. winds have in winter 

 a temperature f'j above the average, humidity 93, and 

 cloud 9 ; but in summer the figures are 5"'2, 82, and 6 

 respectively. One of the most suggestive results is that 

 obtained from the examination of the anticyclone in 

 summer, particularly as regards its calm central space. 

 In the periphery of the anticyclone where winds pre- 

 vail, the cloud accompanying the different winds varies 

 from 3 with S.W. to 5 with E. winds, but in the calm 

 central space the amount is only 2 ; in other words, the 

 space covered by the anticyclone is remarkable for the 

 clearness of its sky, and the central portion is the clearest. 

 Owing to the strong insolation which takes place under 

 these circumstances, the temperature of the whole space 

 covered by the anticyclone is raised 2^'i above the 

 average ; with northerly winds (N.E., N., and N.W.) the 

 excess is, as might be expected, small, being only 0^*5, 

 but with S. and S.W. winds the average excess is 4°'i. 

 The excess in the calm centre is only 1^*3, which is smaller 

 than the excess which accompanies winds from the E., 

 S.E., S., S.W., and W. points of the compass. 



In a review of the weather of Europe during 1868,* Mr. 

 Buchan drew attention to the anticyclone which over- 

 spread a considerable portion of Europe from the 2nd to 

 4th August, as the immediate cause of the hot weather 

 experienced in Great Britain at the time, and which he 

 regarded as the simple result of the widespread high 

 pressure, the comparatively calm atmosphere, the clear 

 sky, the dry air, and the strong insolation which accom- 

 panied these conditions. At the same time, to the west, 

 north, and south-east, pressures were low, the sky clouded, 

 and much rain fell. Since the wind blew out from 

 the anticyclone in all directions, — E. and S.E. winds 

 in Great Britain and France, W. in Austria, and S.W. 

 in Sweden and W. in Russia, — without diminishing the 

 high pressure of the anticyclone, it was suggested that 



* Atlas Miteorologique de I'Obscrvatoire Imperial, Anaee 1868, D. 39, 

 Paris, 1869. 



the high pressure was maintained by air-currents ascen- 

 ding from the regions of low pressure to the west, north, 

 and south-east, and thence flowing as upper currents 

 towards and then down upon the region of the anticyclone. 

 In connection with this point Clement Ley has made 

 some valuable observations on the upper currents of the 

 atmosphere, showing that they flow outwards from the 

 centre of the cyclone, and inwards towards the anti- 

 cyclone. If this view be correct, the centre of the anti- 

 cyclone must necessarily be filled with a slowly descend- 

 ing current. 



Now, it will be observed from Dr. Koppen's inquiry 

 that the centre of the anticyclone is the clearest, on leav- 

 ing which and entering the regions in which winds blow, 

 the sky becomes more clouded — a result strictly in 

 accordance wich a descending current over the calm 

 region of the centre. Again, in the calm centre the tem- 

 perature is lower than round the periphery (except where 

 N.E., N., and N.W. winds prevail, bringing air currents 

 from colder regions, and therefore of a lower tempera- 

 ture), a result admitting of explanation only on the sup- 

 position of a descending current within the central space, 

 since, were there no descending current, the temperature 

 would be hottest in the centre where the atmosphere is 

 clearest and the air stillest. 



We are now, thanks to Dr. Koppen, put in possession 

 of a truly scientific method of discussing wind-observa- 

 tions in their climatic relations, the value of which will 

 be the more apparent when the observations of places in 

 different parts of Europe have been discussed in accord- 

 ance with it. What is now wanted, as regards the diffi- 

 cult but vital question of the observation of the wind, is 

 that truly comparable anemometers be procurable, and 

 that they be placed in situations and positions so that 

 they may fairly record the direction, velocity, and pres- 

 sure of the air-currents which pass over the district where 

 they are placed. 



SCIENCE IN GERMANY 

 {Frotn a German Correspondent) 



MVON JOLLY, in Munich, has recently constructed 

 an apparatus for gas-determination by absorption. 

 Its arrangement is, in general, similar to that of Frank- 

 land's apparatus, but it is distinguished from this, as 

 from all other apparatus hitherto used for gas analysis, 

 by the principle of measurement that is peculiar to it. 

 Measurement is made, not of the changes of volume, which, 

 for example, the air undergoes through absorption of car- 

 bonic acid and of oxygen, but of chanties of pressure, the 

 volume remaining the same. All the air-quantities to be 

 measured are brought to the same volume, through corre- 

 sponding change of pressure, in a measuring vessel, the 

 contents of which must not be known ; while a tempera- 

 ture of o' is produced by surrounding the measuring 

 vessel with snow or ice. Thus, each time the tension is 

 measured under which the air-quantity to be considered 

 assumes that constant volume, before and after absorption 

 of a portion of the mixture. This process has various 

 advantages over those hitherto in use. The calculation 

 of the gas-volumes at normal pressure and temperature is 

 rendered superfluous ; the number of separate observa- 

 tions required is diminished. 



M. Jolly's apparatus is represented in the annexed 

 figure. A is the absorption bell-jar ; it is of nearly 100 c.c, 

 capacity. It is open below, and stands in a pneumatic 

 trough. B is the cylindrical measuring vessel of equal 

 capacity with the absorption jar. By means of a T-shaped 

 perforated glass cock h, the vessels A and B can be con- 

 nected ; they can also be put in communication with the 

 atmosphere by the capillary tube g. B is connected by 

 means of a capillary tube, with a wide glass tube E. At 

 / there is, within the curve, where the capillar)- tube 

 opens, a small tongue of dark glass, i to 2 mm. long, with 



