TRANSACTIONS OF SECTION A. ,549 



Then, again, have we arrived at the extremity of our knowledge of- the surface 

 circulation of the atmosphere ? We know a great deal about the average monthly 

 distribution, but we know little about the instantaneous distribution. It may be 

 that by taking averages we are hiding the very points which we want to disclose. 



Let me remind you again that the thickness of the atmosphere in proportion 

 to the earth's surface is not unsatisfactorily represented by a sheet of paper. Now 

 it is obvious that currents of air in such a thin layer must react upon each other 

 horizontally, and therefore we cannot a priori regard one part of the area of the 

 earth's surface as meteorologically independent of any other part. We have daily 

 synoptic charts for various small parts of the globe, and the Weather Bureau 

 extended these over the northern hemisphere for the years 1875 to 1879 ; but who 

 can say that the meteorology of the northern hemisphere is independent of that of 

 the southern ? To settle that primary question we want a synchronous chart for 

 the globe. As long as we are unable to watch the changes in the globe we are to a 

 certain extent groping in the dark. A great part of the world is already mapped 

 every day, and the time has now arrived when it is worth while to consider what 

 contributions we can make towards identifying the distribution of pressure over 

 the globe. We may idealise a little by disregarding the local peculiarities without 

 sacrificing the general application. I have put in the exhibition a series of maps 

 showing what approximation can be made to an isochronous chart of the globe 

 without special effort. We are gradually extending the possibility of acquiring a 

 knowledge of the facts in that as in other directions. With a little additional 

 enterprise a serviceable map could be compiled ; and when that has been reached, 

 and when we have added to that what the clouds can tell us, and when the work 

 of the Aeronautical Committee has so far progressed that we can connect the 

 motion of the upper atmosphere with the conditions at the surface, when we know 

 the real kinematics of the vertical and horizontal motion of the various parts of a 

 travelling storm, we shall, if the universities will help us, be able to give some 

 rational explanation of those periodic relations which our solar physics friends are 

 identifying for us, and to classify our phenomena in a way that the inheritors of 

 Kepler's achievements associated with us in this Section may be not unwilling to 

 recognise as scientific. 



The following Papers were read : — 



1. On Simultaneous Solar and Terrestrial Phenomena} 

 By Sir N. Lockyer, F.R.S. 



On the Relation of the Rainfall of Scotland to the Sun-spot Periods, 

 1855-98. By A. Buchan, M.A., LL.D., F.R.S., F.R.S.E. 



3. Etudes sur les Depressions Barom^triques a Diverses Haiiteurs. 

 Par L. Teisserenc de Bort. 



II y a dix-sept ann^es maintenant que j'ai montr6 pour la premiere fois que 

 lorsqu'on construit la carte des isobares moyennes des diff^rents mois a diverses 

 altitudes, en partant des pressions et de la temperature au sol, on voit s'effacer la 



{(lupart des maxima et minima de pression. Ces aires entour(5es de courbes fermees 

 ont place a, de simples inflexions des isobares qui se disposent en pente depuis les 

 regions tropicales j usque vers les regions polaires. 



Si I'on considere par exemple la carte moyenne des isobares de Janvier on voit 

 que les grandes aires de haute pressions de Sib^rie et de I'Amerique du Nord, qui 

 commaudent la circulation sur la plus grande partie des continents, sont d(?ja 

 tres amoindries k I'altitude de 2 et disparaissent a peu pres completement a 4,000 m. 



' Printed as an Appendix to the Report o£ the Southport Meeting of the la 

 national Meteorological Committee. 



