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4. — Ojf THE Obsekvatiox of Peeiodical Nattoal Phenomena. 



By John Hopkinson, F.L.S., F.G.S. 



[Read 13th May, 1875.] 



IlfTRODUCTOKY ReMAEKS. 



Attextiox has at various times been drawn to the importance of 

 obtaining a record of observations of certain periodical natiu'al 

 phenomena, conducted universally upon some uniform plan. Meteor- 

 ologists have agreed upon an unifonn system of registration of 

 periodical atmospheric changes, as recorded by the barometer, 

 thermometer, and other instruments ; but hitherto, in this country, 

 only here and there, and -without concert, has the naturalist assisted 

 the meteorologist ia climatological investigations by the aid of a 

 mechanism infinitely more refined and more sensitive to atmospheric 

 influences than any instruments man can constmct. 



Such a mechanism we have in the delicate structure of plants 

 and animals. "With the periodical return of the seasons a series of 

 phenomena takes place, differing in the time of occurrence year by 

 year, but in the same place and under similar conditions usually in 

 the same order. In plants the leaf unfolds, the flower opens, the 

 fruit ripens, and finally the leaf falls. Amongst animals, insects one 

 by one appear, birds arrive and depart, commence and leave off their 

 song, and amphibians, reptiles, and mammals appear and disappear. 



From observations of these and other similar phenomena several 

 Naturalist's Calendars, as they are called, have been compiled, the 

 best known being perhaps the "Calendarium Florae " of Linnaeus, 

 in the ' Amoenitates Academicse,' 1756 ; the calendar di-awn up by 

 Aikin from the manuscripts of the Rev. Gilbert White, first pub- 

 lished, with other observations in Natural History, in 1795, and 

 usually appended afterwards to the ' Natural History of Selbome ; ' 

 Markwick's calendar of observations made at Catsfield, near Battle, 

 first published in the 1802 edition of this work ; and that given by 

 Jenyns in his 'Observations in Natural History,' the record of 

 notes which he made at Swaffham Bulbeck, a village a few miles 

 beyond Cambridge. 



The work of which this carefully compiled calendar forms a part 

 was published in 1846. At the meeting of the British Association 

 for the Advancement of Science held at Cambridge in the previous 

 year, a report of a Committee, " Appointed for the purpose of Re- 

 porting on the Registration of Periodical Phenomena of Animals 

 and Vegetables," was presented, the Report consisting mainly of a 

 translation (revised and enlarged by the Kev. L. Jenyns and M. de 

 Selys-Longchamps) of a series of ' Instructions for the Observation 

 of Periodical Phenomena,' previously prepared at Brussels by M. 

 Quetelet and other Continental naturalists. 



This report was a most valuable contribution to the subject, but 

 it is only now, after a lapse of thirty years, that it seems likely to 



VOL. I. PT. II. 3 



