540 SCIENTIFIC RECORD FOR 1883. 



and not in the polar regions, since the former has an area of 79 and the 

 latter 8 per cent, of the whole hemisphere. A further extension of the 

 simultaneous observations initiated by General Myer [probably the first 

 were by the present writer in 1869], although very advantageous for a 

 single continent, has, he thinks, no value for a whole hemisphere, and 

 may even lead to error, since the high temperatures during day-time are 

 much more important than the cooling of the earth at night-time, and 

 these on the simultaneous system are not given for at least one-half 

 of the hemisphere. Neither hydrometry, nor dynamic or climatic prob- 

 lems can be studied by means of one simultaneous observation. {Z. 0. 

 G. M., xvn, p. 200.) 



Januschke exposes the advantage of the study of the so called level 

 surface or surfaces of equal barometric pressure in the interior of whirl- 

 winds corresponding to the similar study by Hann, Ferrel, and others, 

 on the general circulation of the atmosphere over the earth. The influ- 

 ence of the temperature and moisture as affecting density of the air is 

 easily taken into account, but the influence of the rotation of the earth, 

 which becomes more perceptible in the higher latitudes, requires more 

 complicated considerations, but by considering the propositions deduced 

 by the mathematicians and utilizing the graphic presentation he attains 

 to a fairly clear view of the atmospheric relations. (Z. 0. G. M., xvn, p. 

 136.) 



Dr. F. Augustin has studied a relation between diurnal periodicity of 

 atmospheric pressures and temperatures, as shown by observations for 

 twenty years at Prague. He finds, in general, that pressure rises when 

 the temperature changes are greater and falls when they are less, and 

 that the changes in pressure are greater in proportion to the rapidity 

 and duration of the changes in temperature. The oscillations of the 

 barometer by day are greater than by night because the temperature 

 rises from maximum to minimum much more rapidly than it falls. (Z. 

 0. G. M., xvn, p. 330.) 



Hann has collected together what little is known of the diurnal 

 periodicity of meteorological phenomena on the Rocky Mountain pla- 

 teau. He finds the diurnal barometer curve in summer quite analogous 

 to that of the interior of the Asiatic continent and directly opposed 

 to that upon the mountains of corresponding altitude. It is therefore not 

 the absolute altitude, but the local position on the flanks or the summit 

 of a mountain that materially influences the daily barometer curve. 

 This curve is on high plateaus and in high valleys the same as on the 

 low lands, and the magnitude of the diurnal amplitude is remarkably 

 independent of the altitude. The same is true of the diurnal tempera- 

 ture curve. The stations of great diurnal temperature oscillations are 

 not those of greatest barometric oscillations. According to Hann, with 

 the morning increase of temperature there flows from the air above a 

 valley a certain proportion towards the flank of the mountain, to which 



