42 



On Variations of the Barometer in India. [May 11^ 



When we consider the ranges of the oscillations at the different sta- 

 tions we find them to be as follows : — 



Stations. 



1st Max. to Min. 



Min to 2nd Max. 





in. 



in. in. 





0-397 



0-146 or 0-600?^ 





0-430 





Cape of Good Hope 



0-305 



0-294 





0-343 



0-475 



Bogoslowsk 



0-269 



0-410 



Makerstoun 



0-189 



0-145 





0-070 



0-050 ? 





0-083 



0-054 





0-069 



0-059 





0-066 



0-103 



Thus Simla, though in nearly as high a latitude as the Gape of Good 

 Hope, belongs by the range to the tropical series. 



It is of much importance to observe that we have here to deal with 

 the great atmospheric movements experienced in high latitudes. Thus 

 the change of observed barometric height from minimum to maximum 

 at Gatherinenburg was nearly 0*6 inch ; while at Makerstoun, though 

 the variation of the daily mean pressure was less than at the other 



Postscript, received 1st July. — Since writing the preceding note I have examined 

 the barometric observations made at Sitka (latitude 57° 3' N., longitude 14"^ 58"" east 

 of Greenwich). I find that there are two minima and two maxima within the week 

 under consideration ; these are as follow : — 



Local 

 Mean Time. 



Daily Mean. 



Range. 



Local 

 Mean Time. 



Observed 

 Height. 



Range. 



d h 



in. 



—. 



m. 



d h 



in. 



in. 



Mar. 31 18 



Min. 29-277 





31 22 



29- 123 









0-483 







0-720 



Apr. 1 21 



Max. 29-760 





1 22 



29-843 







0-269 







0-531 



„ 2 19 



Min. 29-491 





2 20 



29-312 









0-824 







1069 



„ 4 12 



Max. 30-315 





4 11 



30-381 





It will be seen that while the first minimum is not shown at any of the other 

 stations after March 31^ 0^ and the first maximum occurs twelve hours later than at 

 Bogoslowsk, yet the second minimum occurs nearly at the same local hour as at 

 the Asiatic stations, and the second maximum at the same local hour as at the 

 Cape of Good Hope. The movements of the mercury are still larger than in any 

 of the other cases, the change from the minimum, April 2^ 20^, to the maximum 

 observation, 4^ 11^ being upwards of one inch. The whole series of facts leaves, 

 it appears to me, no doubt that this great movement is connected with the same 

 cause which produces the comparatively small variations within the tropics ; and it 

 may be noted that as we approach the poles the amount and irregularity of the 

 barometric oscillations seem to increase, as in the case of the magnetic variations. 



* These ranges refer to the maximum after 5^ 0''. 



