MEAN SCOTTISH METEOROLOGY. , 267 



PAET III. 



Thirty-one Chronological Tables op Mean Scottish Meteorology, Month by 

 Month, from 1856 to 1887 inclusive, — Explanations of. 



These Tables are derived by immense condensation from the bi-diurnal observations 

 taken voluntarily and with remarkable assiduity, by the observers of the Scottish 

 Meteorological Society, at 55 of their stations scattered over the whole country of 

 Scotland (Highlands and Islands included) ; and computed by order at the Eoyal Observa- 

 tory, Edinburgh, for the purposes of the Kegistrar-General of Births, Deaths, &c. in 

 Scotland, for every month in every year from 1856 to 1887 inclusive. 



1. Historic Origin of the Data. 



When the Astronomer in charge of the Royal Observatory, Edinburgh, was first 

 called on by Government in 1858 to begin his part in the above Meteorological calculations 

 for the purposes above stated, he found a generally excellent system already organised, 

 and worked for two years by the late Dr Stark, then the enthusiastic Secretary to the 

 Scottish Meteorological Society, as well as a scientific and responsible officer in the depart- 

 ment of the Registrar General for Scotland. 



Continuing that system, the ordinary instrumental corrections were carefully applied 

 at the Observatory, and monthly means, collected from the bi-diurnal observations of all 

 the stations, were exhibited and printed, first for each station by itself, giving all its 

 individual characteristics untouched; and next for the mean of all the 55 stations ; or 

 for something very like the one geographical and physical centre of the whole Caledonian 

 country. For, such an extensive condensation of the records of many instruments and 

 many observers would, it was hoped, possess a certain solidity of accuracy ; and justify 

 confidence in it to a greater extent than any single observer, either in town or country, 

 could ever expect to attain to. 



But there was still no opportunity of ascertaining for any month in any year, how far 

 that season might be an extraordinary one, as touching any, much more all, the usual 

 meteorological items of study. The historical element as to annual recurrences, agreements 

 or disagreements, and cyclical rises and falls of many years, was then in fact entirely 

 wanting ; and could only be expected to be supplied by continuous observation united 

 with undeviating registration of them through many years. In a manner however 

 quite suitable for a Government Observatory to engage in, and become responsible for. 

 To supply this confessed want therefore, the Astronomer specially applied himself; and 

 entered each month's means for the collected country in ledgers, as the years went by, in 

 the form best adapted for successive chronological digests being taken, for every succeed- 

 ing accumulation of years from the beginning of the activities of the Scottish Meteoro- 

 logical Society, down to the latest passing period. 



At first, from the frequently very great differences of the calendar months of one year, 

 from those of another, even when the Mean of all the stations, or of the whole country, 

 was concerned, these chronological means used to vary rather violently from each other. 



