362 IMPORTANCE OF REGISTERS 



from which the mean is calculated. When the ob- 

 servation has been made in only a single instance, the 

 annexed date has been entered under the head of 

 mean, as a place which it is entitled to hold till other 

 observations of the same phenomenon point out 

 what its exact value is in this respect. When only 

 two observations have been made, and both these 

 have occurred, as in a few instances, upon the 

 same day, the entry has been registered under the 

 same head, with the figure 2 annexed to it. When 

 but two observations have been made, and they have 

 occurred on two consecutive days, these two days 

 have been bracketed together under the head of 

 mean. Lastly, it may be observed, that all the 

 entries under one date, to whatever class of pheno- 

 mena they may belong, are bracketed together in 

 such a manner that the eye may catch, at one glance, 

 the several coincidences as they successively occur, 

 without having to sort them out from the first of the 

 three columns above spoken of. 



(25.) Perhaps the most perfect portion of the 

 calendar, in respect of the number of years in which 

 the observations have been repeated, is that which 

 relates to the periods, at which different birds com- 

 mence song, and at which our principal summer 

 visitants make their first appearance. And these 

 phenomena are also amongst the most important, in 

 respect of the indications they afford of the time of 

 year, and the character of the season. Many of the 

 observations, likewise, connected with the leafing of 

 trees, and the flowering of the more common plants, 

 are perhaps sufficiently numerous, in certain in- 



