Chemistry and Physics. 151 



While for single years the amount of variation in the time 

 of grape harvest may vary by many days, and for the five years 

 lustra reaches even three weeks, yet for the smoothed out 

 lustra averages the extremes are about a week earlier than the 

 average for the minima and a week later for the maxima times 

 of harvest. A comparison of these periods with similar periods 

 of rain-fall and temperature shows that in general the early har- 

 vest period is identical with that of high temperature and small 

 rain-fall, and conversely the times of late harvest and low tem- 

 perature and excessive rainfall occur together. By means of 

 the recorded dates of the grape harvest it is possible therefore 

 to trace back to about the year 1400 for Central Europe the 

 periods of warmth and dryness, and cold and excessive wetness. 

 The relation to the glacier changes are still closer. 



The occurrences of severe winters have been catalogued still 

 further back, and Bruckner commences his list (using that of 

 Pilgram) with the year 800, but thinks that the records before 

 the year 1000 are of little value. He finds finally that for the 

 period 1020 to 1190, there exists a 34 years oscillation ; from 

 1190 to 1370, a 36 years period ; from 1370 to 1545, a 85 years 

 period ; from 1545 to 1715, a 34 years period ; and from 1715 

 to 1890, a 35 years period. 



An average time of about 35 years is, then, found to inter- 

 vene between one period of excess or deficiency of heat and 

 the next, with the opposite relative condition of moisture 

 accompanying ; and this shows itself in all of the various data 

 and methods which have been used in considering the question. 



Princeton, K J., Dec. 1890. 



SCIENTIFIC INTELLIGENCE. 

 I. Chemistry and Physics. 



1. On the Law of Osmotic Pressure. — Planck, in applying 

 the general conditions of thermodynamic equilibrium to the case 

 of a dilute solution separated from the pure solvent by a mem- 

 brane which allows only the solvent itself to pass and not the dis- 

 solved substance, finds that when equilibrium results, there must 

 exist on the side of the solution a greater hydrostatic pressure 

 than on the side of the solvent. And moreover, that this neces- 

 sary pressure-difference increases proportionally with the number 

 of dissolved molecules in a unit of volume and with the absolute 

 temperature ; the factor of proportionality being the same as for 

 gases. But this is the law of osmotic pressure as originally stated 

 and experimentally established by van't Hoff. So that this law 

 now appears as a direct consequence of the fundamental princi- 

 ples of thermodynamics; and not only the law itself, but also all 



