434 Dr. Echc. Jaderin — On Variations of Climate. 



differed greatly from the present. The change referred to must, 

 therefore, be accepted as a fact, but as regards its nature there are 

 several pi'obabilities to contend with ; for instance, whether it can 

 be traced in a short span of time or at all events in historical times, 

 whether it is confined only to parts of, or to the whole earth, whether 

 it is limited to long or short periods, and, finally, whether the change 

 can be shown to be still continuing in the same direction. 



The latter question is of course of the highest general interest, as 

 it is closely connected with the history of the earth's development 

 from its first commencement as a planet to its final stage. 



In recent times the copious meteorological materials now at our 

 disposal have been analysed, in order to demonstrate the change in the 

 climate within briefer spans of time. Jt is well known that glaciers 

 are subject to changes in their extension, viz. that during certain 

 periods they advance, and during others retreat beyond their normal 

 limits. Naturally, the cause of this should be sought in the climate, 

 and now, in fact, Forel, Richter, and Lang have demonstrated that 

 this phenomenon in the Alps corresponds with a similar periodicity 

 of temperature and fall of moisture. But the variability of these 

 meteorological factors do not only occur in the Alps, as in 1887 

 Bruckner demonstrated that a periodicity of the rainfall occurs in 

 nearly all countries of the Northern Hemisphere. Of this proof is 

 not only furnished by the rain-gauge, but also by the changes of 

 great duration which take place in rivers, lakes, and in the sea. In 

 the Southern Hemisphere too — as far as we are able to judge from the 

 scanty material at our disposal — a corresponding variability occurs. 1 

 In fact, according to the latest investigations of Prof. Siegers, of 

 Vienna, upon the level of water in oceans and lakes, this variability 

 of rainfall occurs over the whole surface of the globe. 



The temperature of the air, too, is subjected to periodical variations 

 although in a less pronounced degree. On this point it is of interest 

 in winter to study the period during which rivers and lakes are 

 frozen over, as it has been shown that the periodicity coincides 

 with that of the Alpine glaciers. 



For the investigation of the circumstances indicated, we have at our 

 disposal material collected at some 500 different meteorological 

 stations, comprising 25,000 years of time of observation, and on 

 the basis of the same we are enabled to declare that the climate 

 of all countries in the world is at a certain time and manner 

 subjected to a change, and that the areas where this is not the 

 case are very limited, indeed they embrace only some coast lines. 

 The varaibility becomes also the more pronounced the further inland 

 we advance. 



In the present century the years 1815, 1850, and 1881 mark 

 about the middle of three relatively wet periods, and the years 1830 

 and 1860 the middle of two correspondingly dry periods. 



It would be of interest to know whether the climatic changes are 

 regularly periodical or whether the length of the period suffers any 



1 Vide Stanley's report as to the changes of water-level in the Great Lakes since 

 his last visit. — Ed. 



