200 



Instructions for Making and Registering 



[Jan^ 



ward, as that of a Medal for instance, should the funds of the Institution 

 admit of it. 



With a view, however, to the better determining the laws of the 

 diurnal changes taking place in the atmosphere, and to the obtaining a 

 knowledge of the correspondence of its movements and affections over 

 great regions of the earth's surface, or even over the whole globe, the Com- 

 mittee have resolved to recommend, that four clays in each year should 

 henceforward be especially set apart by Meteorologists in every part of 

 the world, and devoted to a most scrupulous and accurate registry of 

 the state of the Barometer and Thermometer; the direction and force of 

 the Wind ; the quantity, character, and distribution of Clouds ; and 

 every other particular of weather, throughout the whole twenty-four 

 hours of those days, and the adjoining six hours of the days preceding 

 and following.* The days they have been induced to fix on and recom- 

 mend for these observations are, the 21st of March, the 21st June, the 

 21st September, and the 21st December, being those or immediately ad- 

 joining to those of the Equinoxes and Solstices, in which the Solar in- 

 fluence is either stationary, or in a state of most rapid variation. But 

 should any one of those list days fall on Sunday, then it will be under- 

 stood that the obserualio?is are to be deferred till the next day, the 22d. 

 The observation at each station should commence at six o'clock a. m. 

 of the appointed days, and terminate at 6 o'clock p. m. of the days fol- 

 lowing, according to the usual reckoning of time at the place. During 

 this interval, the Barometer and Thermometer should be read off, and 

 registered hourly, and the precise hour and minute of each reading 

 should be especially noted. 



For obvious reasons, however, the commencement of every hour- 

 should, if practicable, be chosen, and every such series of observations 

 should be accompanied by a notice of the means used to obtain the 

 time, and, when practicable, by some observation of an astronomical 

 nature, by which the time can be independently ascertained within a 

 minute or two.f As there is scarcely any class of observations by which 

 meteorology can be more extensively and essentially promoted, it is 

 hoped that not only at every station of importance in this colony but 

 over the whole world, and on board ships in every part of the ocean, 

 individuals will be found to co-operate in this inquiry. Every commu- 



* This is necessary by reason of the want of coincidence of the day in different parts of 

 the globe, arising from difference of longitude. In order to obtain a complete correspon- 

 dence of observation for twenty-four successive hours over the whole globe, it must be 

 taken into account that opposite longitudes differ twelve hours in their reckoning of time. 

 By the arrangement in the text the whole of the astronomical day (from noon to noon) is 

 embraced in each series, and no observer is required to watch two nights in succession. 

 + For example, the first appearances and last disappearances of the Sun's upper and lower 

 border, above and below the sea-horizon, if at sea or on the coast,— or on land the exact 

 length of the shadow of a vertical object of determinate length on an horizontal level, at a 

 precise moment of time, (not too near noon), &c. 



