APPENDIX A. 

 A RECORD IN NATURE-STUDY. 



EXPLANATION OF FIG. 7. 



The three charts above the landscapes record graphically the observations 

 of certain meteorological phenomena for April, May, and June. The narrow- 

 vertical strips are eighteen inches long and represent (arbitrarily) the day of 

 twenty-four hours. Upon the lower part of the strips (blue on the chart) is 

 measured off the correct proportion to represent the length of night. What 

 remains above (yellow on the chart) represents the daylight. Upon the latter 

 the cloudy days and the rainy days are represented respectively by the lighter 

 and darker shades of gray. The straight horizontal line represents the freezing- 

 point. Above and below this, at either end, the edge of the card is graduated 

 as a thermometer. The upper zigzag line shows the curve of mean tempera- 

 ture, and the lower one shows the barometric curve, the card at one side being 

 scaled as a barometer. 



Between the two lines, arrows are placed which indicate the direction of 

 the wind. Various relationships are easily worked out. The wind that 

 oftenest accompanies clouds, rain, or sunshine; the combination of events 

 that accompanies the low or the high temperatures; the rise and fall of the 

 barometer, and the rise and fall of temperature ; the relation of both these 

 curves to cloudiness and rainfall ; the gradual change in the length of day and 

 night, absolute and relative; the bearing of all combined upon the landscape 

 pictured below — these and many other comparisons may be made at a glance, 

 and all reveal the close interdependence of the phenomena of nature. 



Above these charts, by means of the skiameter, the relative distribution of 

 sunshine for the latitude of Chicago is shown for each month. Since the 

 intensity varies with the distribution, and the ratio of the April rectangle is 

 to that of June as 15 to 12, it follows that the intensity of the latter month is 

 one and a fourth times the intensity of the former. In other words, the sun- 

 shine that does duty on a fifteen-acre field in April will cover only about 

 twelve acres in June. 



At the left of the chart, three drawings show the slant of the sun's rays 

 for each of the three months, and also the area that each beam covers. 



The Mason jars below the landscape illustrate graphically the rainfall. 

 Each jar contains the quantity of water that fell in a month on an area of 

 twenty-four square inches, January being on the left. The upper row shows 

 the average for each month during a period of thirty years. The lower row 

 shows the rainfall by months for the year 1901. The upper row shows what 



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