816 Abstract of Meteorological Tables. [Dec. 



XIII. — A Comparative view of the daily range of the Barometer in dif- 

 ferent parts of India. By James Prinsep, Sec. As. Soc. $c. 



The friends who have for the last two years favored me with 

 copies of their Meteorological Registers, have doubtless accused me 

 of a most ungracious requital of their labours, in the long slumber 

 to which they have apparently been devoted in my editorial escru- 

 toire ! Such is not absolutely the true state of the case ; but the num- 

 ber attached to the accompanying plate* will, I fear, testify against me 

 to the extent of having kept back for nearly a year, the curious facts 

 that had been elicited from the possession of so many valuable re- 

 cords of the weather. 



The fact is, that the prompt attention with which my appeal was 

 answered by observers of the weather in numerous parts of India, 

 served as a check to the immediate publication of the materials sup- 

 plied. The very voluminous dimensions of such registers, and their 

 dry and unperusable nature, even by the few who would like well to 

 consult them, set me about contriving some method of condensing 

 their results into convenient compass, and exhibiting them to the eye 

 in a manner more perspicuous than could possibly be accomplished 

 by a mass of mere figures. 



The usual form of a diagram of zigzag lines from point to point 

 would apply tolerably well to a series of single daily observations, 

 taken at a particular hour, and would trace out in a gently undulat- 

 ing curve, the course of annual variation ; but if made to embrace the 

 double daily oscillation, now well known to be steadily pursued by the 

 Barometer in intertropical climates, it was evident that the alternations 

 would be too confused on a small scale to be followed pleasantly by the 

 eye. A slight modification suggested itself, as calculated to remove 

 all objections to this mode of displaying the phenomena, without taking 

 in any degree from the accurate notation of the fixed points of obser- 

 vation, while it represented more palpably the amount of daily oscil- 

 lation. The modification to which I allude will be readily understood 

 by inspection of Plate XIV. It consists in breaking the connection 

 between the consecutive days, and merely laying off, in short parallel 

 lines, the interval between the maximum and minimum readings of the 

 instrument. The proximity of the lines enables the eye to fancy 

 an imaginary line drawn centrally through them to represent the 

 mean course, without the necessity of drawing it, while errors of the 

 tenth of an inch, so liable to occur, and so difficult of detection in a 

 series of figures, became at once obvious and remediable. The chief 

 * It was first printed as Plate IX. subsequently altered to XIV. 



