6 E. Loomis— Results from an examination of the 



In winter the warmest wind at Philadelphia is found to blow 

 from a direction S. 40° E., while in summer it blows from the 

 S.W. The former direction takes us to the Gulf Stream at 

 about its nearest point, and at a distance of 250 miles. In 

 summer the warmest region within 400 or 500 miles of Phila- 

 delphia lies in a direction S. 30° W., while the warmest wind 

 blows from a point 15° more westerly. On the whole, the ob- 

 servations indicate that both the warmest and coldest winds at 

 Philadelphia blow pretty nearly from the regions of greatest 

 heat and cold, but there is reason to suspect that these direc- 

 tions are not quite coincident. 



From the table of monthly minima of temperature at New 

 Haven given in my former article, (this Jour., vol. ix, p. 7) it 

 will be seen that the average monthly minimum is 25° below 

 the mean temperature of the corresponding month. The table 

 last given shows that a small portion of this effect (viz. 5°) ma}^ 

 be ascribed to the influence of the direction of the wind, but there 

 remains unexplained four-fifths of the whole efi'ect which is to 

 be ascribed to the influence of other causes. 



The preceding table shows that both in summer and winter 

 the force of vapor at Philadelphia is greatest with the same 

 wind which brings the highest temperature ; and it is lowest 

 with the wind which brings the lowest temperature. The de- 

 viations from this rule are so small as to render it probable that 

 the discrepancies would entirely disappear in the means of a 

 long series of observations. 



Since cold air has a greater density than warm air, and dry 

 air has a greater density than vapor of water, it might be ex- 

 pected that the wind which brings the lowest temperature and 

 the least vapor, would bring the highest pressure. We see. 

 however, from the preceding table that such is not the case. In 

 winter the highest pressure comes with a wind from the N.E., 

 or perhaps N. 55° E. ; while in summer the highest pressure 

 comes with an east wind, which directions are distant more 

 than 90° from the coldest quarter of the horizon. So, also, in 

 winter, the lowest pressure comes with a S.W. wind, and in 

 summer with a west wind, both of which directions are quite 

 distant from the warmest quarter of the horizon. It seems 

 probable that the excess of uressure which accompanies an east- 

 erly or N.E, wind is but the result of the high barometer 

 which usually precedes a N.E. storm. 



Diurnal inequality in the rain-fall. 

 In my former article (this Jour., vol. x, p. 3) I noticed a di- 

 urnal inequality in the progress of storms and was hence led 

 to infer that there must be a diurnal inequality in the fall of 



