The difference is not great. For Stockholm the winter has grown warmer, the autumn colder, for London the winter warmer and so slightly also the summer, but spring and autumn a trifle colder, and for Paris the summer a little warmer while the autumn is considerably colder. Lund shows the least variation. The winter has grown 0.4° C. (0.72° F.) warmer and the summer colder by the same amount. The annual mean remains nearly constant, only slightly increased, but the climate is become more marine. (This is hardly apparent from the figures cited as far as Paris is concerned.) From Tycho Brahe’s observations of the number of days when snow or rain fell in the place where his observatory was situated on the island Hven in Öresund not far from Copenhagen, Ekholm has calculated that the temperature there during the time 1582–1597 was 1.4° C. (2.5° F.) lower in February and 1° C. (1.8° F.) lower in March than in later years (1881–1896). On the other hand the first autumn frost occurred at the same time as now and the same was the case with the last frost in spring, so that the temperatures on these dates in autumn and spring were nearly identical at the end of the sixteenth century and now. Ekholm drew the conclusion that the climate is become more marine. Hildebrandson makes the objection that Tycho Brahe’s observations were confined to an abnormally cold period judging by the tables Speerschneider has prepared showing the ice formation in Danish navigable waters. Nine out of the sixteen years in which Tycho Brahe gathered his data were notable for abnormally cold winters, while only nineteen out of the hundred years composing the sixteenth century were characterized by equally severe winters. Thus, the conclusion is not warranted that the winters of the sixteenth century as a whole averaged colder than those of the nineteenth. Later investigations (in 1917) in regard to the dates when the ice would break up in Lake Mälar at Vesterås, in Neva River at Petrograd, and in Dwina River at Riga, have led Ekholm to believe that he has found a periodicity in winter temperatures of not less than 212 years, a conclusion which would agree with Speerschneider’s statistics. If so, we are at present living in a period remarkable for its mild winters while a series of extremely severe winter seasons occurred at the time of Tycho Brahe. This law would also have a bearing on the preceding table of temperatures in Stockholm, Lund, London, and Paris as a succession of severe winters came around in the beginning of the nineteenth century while the reverse is true towards its end. On the whole climatic variations during historic time have been insignificant, if present at all, provided we extend our comparisons over two or more centuries. Such is also the opinion of Hildebrandson.