METEOROLOGICAL. OBSERVATIONS. 43 



The tabulated results of these reductions, and their projected curves, accom- 

 pany this Report for the inspection of the Meeting. The curves are pur- 

 posely projected on a large scale (too large for publication) to afford room 

 for a minute examination and analysis of their several inequalities, with a view 

 to the possibility of tracing the progress of subordinate undulations or of 

 cross waves ; and each has been made by Mr. Birt the subject of particular 

 and careful discussion, the results of which he has embodied in the form of 

 notes on the, several terms. Many of these contain remarks of much interest, 

 especially that on the December term of 1836, which fortunately comprises 

 the ascending branches of the barometer curves during a remarkable storm, 

 as well as others, which however must be reserved for the final report of your 

 Committee, which it may be confidently stated will be ready for presenting 

 at the next Meeting. 



Meanwhile the annexed letters from Mr. Birt will serve to give the Meet- 

 ing somewhat more than a general idea of the direction which the inquiry is 

 taking, and contain some suggestions relative to a system of concerted ob- 

 servation excellently well adapted to the tracing of atmospheric waves across 

 a tract of country, to which, as well as to his offer to undertake the necessary 

 correspondence, your Committee desires to direct the especial attention of the 

 Meeting. (Signed) J. F. W. Herschel. 



" Metropolitan Literary and Scientific Institution, June 1, 1841. 



" Dear Sir, — I exceedingly regret that I have been unable to forward you 

 the packet containing the projections, &c. of the American observations until 

 so long after the time mentioned in my last. I was extremely anxious not to 

 omit any point that suggested itself in carefully looking over the projections 

 and tables, and having completed this, I hope the packet will reach you in 

 sufficient time to enable you to draw up the report for the Meeting without 

 inconvenience. 



" The remarks I have to offer I have thrown in the form of notes to each 

 sheet of the projections. In these notes I have taken very little, if any, no- 

 tice of the curves south of the United States, the Bahamas, &c. I may how- 

 ever remark here, that the curves at the Bahamas generally differ from those 

 of the United States ; and as they are situated near the northern border of 

 the torrid zone this difference is remarkable and interesting, as it indicates 

 different systems of oscillation peculiar to the zones. Numerous observations 

 from tlie Bahamas, and the West India islands generally, would be highly in- 

 teresting. 



" One point which I have glanced at in the notes appears to me interesting 

 and worthy of attention in future observations and discussions of this kind, 

 namely, the appearance of the diurnal oscillation when the extent of oscilla- 

 tion at the station is small, for instance under O'l inches. Generally as the 

 oscillation increases the diurnal oscillation becomes obscured. 



" With respect to the tables and projections, I have very carefully examined 

 them, and I am not conscious of any errors existing ; the reductions I have 

 carefully verified in every instance, and the amount of error in the projections 

 is not greater than '0005 in the readings of the barometric altitudes ; this 

 amount of error arises from hygrometric causes. 



" With respect to the increase of oscillation, as mentioned in the concluding 

 remarks to the notes on the projections, it appears that the stations from 

 which observations have hitherto been obtained are too few to derive correct 

 conclusions relative to it. Probably, on one or two occasions that may be 

 fixed on for future observations, a number of gentlemen may undertake a 

 scries of observations of the barometer, having especially this object in view, 



