1822.] made at Crumpsall, in Lancashire, 89 



an hour before sun-rise, in the ordinary course of things, A 

 knowledge of these facts would enable those who have the 

 leisure, and are so disposed, to ascertain the daily extremes and 

 means of temperature, with a tolerable degree of precision, if 

 the invention of self-registering thermometers did not offer a 

 much more ehgible means of procuring such information; but 

 the case is very different with regard to atmospherical pressure, 

 as it is quite uncertain at what periods the maxima and minima 

 may take place. It, therefore, rarely happens, that the true 

 daily extremes and means of pressure are obtained from the very 

 small number of observations that are made in the course of the 

 natural day by the majority of meteorologists ; and it would be 

 difficult, if not impossible, to lay down a plan for conducting such 

 observations, with the instruments that are commonly used for 

 this purpose, that would be sufficiently exact and convenient for 

 general adoption. 



These considerations, together with the desire of doing some- 

 thing towards establishing a more regular and efficient mode af 

 observing than any of those which are at present in use, induced 

 me to turn my attention more particularly to the nature of the 

 instrurments employed ; when a little reflection convinced me 

 that if a good self-registering barometer could be obtained, it 

 would assist me in my project very materially. 



Shortly afterwards, having procured a self-registering baro- 

 meter, I placed it by a common upright one, in a room on the 

 second floor, about 15^ feet from the ground ; and after compar- 

 ing them, and finding that they corresponded exactly, at 12 

 o'clock on the night of Sept. 30, I commenced the preceding 

 observations, which were made witli the common barometer ; 

 one or two gentle vibrations being given to the mercury, for the 

 purpose of disengaging it more effectually from the tube when- 

 ever an observation was taken. 



The weather was stormy, with frequent showers through the 

 day ; a strong gale from the W. prevailing till two o'clock, p. ra. 

 when it shifted to the NW, from which point it continued to 

 blow with violence till midnight. 



The extremes by the common barometer were 29*610, and 

 29*195, the mean of which is 29*402, the range being -415, and 

 the mean of the 25 observations is 29*347. 



The following tables contain the results of observations taken 

 at the most convenient hours before noon and afternoon. 



