PHILOSOPHICAL TRANSACTIONS 
XV. Discussion of Meteorological Observations taken in India, at various heights, 
embracing those at Dodabetta on the Neelgherry Mountains, at 8640 feet above 
the level of the sea. By Lieutenant-Colonel W. H. Sykes, F.R.S. 
Received January 12, — Read March 21, 1850. 
In the year 1835 the Royal Society did me the honour to publish the results of six 
years’ meteorological observations, taken by me on the elevated plateau of the 
Dukhun (Deccan) from 1825 to 1830, both years inclusive ; my chief object being to 
illustrate the diurnal oscillations of the barometer as indicative of the periodic tides 
(if they may be so called) of the atmosphere. I showed that in many thousand ob- 
servations, taken personally, there was not a solitary instance in which the barometer 
was not higher at 9 — 10 a.m. than at sunrise; and lower at 4 — 5 p.m. than at 9 — 10 
A.M., whatever the state of the weather or the indications of the thermometer or hygro- 
meter might be-, nor was there a solitary instance in 1830, during which year only I 
took systematic night observations, and observed at the turning-points every five 
minutes, in which the maximum nocturnal tide was not higher at 9 — 10 p.m. than at 
4 — 5 P.M. The 4 — 5 a.m. minimum tide was less regularly noticed than the other 
three tides ; but nevertheless sufficiently often to render it perfectly clear, that in the 
twenty-four hours there were two minima as well as two maxima of pressure in 
twenty-four hours. I had the advantage at times of carrying on my observations in 
the six years, at a mean elevation of 1800 feet, simultaneously with observations 
made in Bombay at the level of the sea, and at Mahabuleshwur at 4500 feet above 
the sea. These simultaneous observations for limited periods led me to remark, that 
the amount or range of the diurnal oscillation between the maximum and minimum 
hours did not correspond at the different elevations. At the level of the sea in 
Bombay the range between 9 — 10 a.m. and 4 — 5 p.m., appeared generally to be less 
than the range between the same hours in Dukhun (Deccan) at 1800 feet above the 
sea; but at Mahabuleshwur, at 4500 feet, the range was constantly less than in 
Bombay or on the plateau of the Deccan. Not having had further means of pro- 
secuting inquiry into the fact, it was with much interest I remarked that the orders 
of the Court of Directors of the East India Company had been carried out by the 
astronomer at Madras, and meteorological observations taken for a whole year at a 
MDCCCL. 2 Q 
