Outlines of the Geography of Plants (1846)

Seitenzahl:

338

Gewicht:

494 g

Erschienen bei:

Cambridge Scholars Publishing

Kurzbeschreibung

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: It has also been tried to determine the time of day when the temperature is equal to the mean daily temperature; but all attempts of this kind only in some degree approach the truth, for it is easy to see that the various lengths of the day must cause a great difference in this. And these times must also vary according to the latitude, as well as the length of the day. In northern countries, where in summer the temperature is frequently as high, and sometimes higher than in the tropics, this great degree of heat must be explained by the length of the day, for in the tropics the day lasts only twelve hours. The sun there rises about six o'clock, while with us it appears in summer by three A.m., and does not set until eight o'clock, and, therefore, shines more than five hours longer than within the tropics. On account of this greater length of the day, the times of the maxima and minima, as well as of the approximate means of daily temperature, must vary in different zones, and the greatest difference will be found in the extreme north and extreme south. Thus in Lapland, at the season when the sun is never visible above the horizon, the highest temperature of the day is just at morning. The mean temperature of single days being found, we may go on to determine the mean annual temperature, which is at the same time the mean heat of the place where the observations are made. The mean temperature of the year is very easily found, either by taking the average of all the daily observations, or by dividing the sum of the daily means by the number of days. In tropical countries the observations of one year are sufficient in order to learn the mean heat of a place, for the progress of daily and monthly temperatures is there remarkably regular; but in the temperate, and especially in...

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Mehr von:  Franz Julius Ferdinand Meyen, Cambridge Scholars Publishing