Diagrams to Illustrate the Effects of the Weather. 151 



claim a very great superiority for our tables over any others that 

 have been made. 



(2) The very full details of the weather of every year during 

 which the observations have been taken ; these details being taken 

 with verified instruments, and with the exactness required by the 

 Meteorological Society. 



Referring now to the diagram, the lines at the bottom are intended 

 to represent the general state of the weather ; in the upper (double) 

 one the difference of the temperature of each week from the mean of 

 that week for the previous ten years is indicated by a black line when 

 below it, and a shaded line when above it. Thus if the temperature 

 of any particular week was 5° below the mean of the previous ten 

 years a black line of suitable length would be drawn, if above it a 

 shaded one. 



The next line indicates the amount of sunshine. As this has not 

 been observed for ten years, the differences from the means cannot be 

 given, but I have indicated the percentage of the proper amount dtie, 

 which is always done by a shaded line, as the heat is intended to be 

 shown. Of course the shaded spaces will not indicate the actual 

 number of hours of sunshine, nor the same number of hours (if the 

 shaded lines happen to be of the same length), but merely the 

 proportion of sunshine which was experienced in that week. Thus, 

 if in one week we had had fifty out of one hundred hours due, and 

 in another twenty-five out of fifty hours due, these two quantities 

 would be indicated by lines of equal length, as in both cases we had 

 half the quantity due. 



The lower (double) line indicates the rainfall, black indicating 

 that the amount was greater than the mean, and shaded that it was 

 less, as the greater the rainfall the greater the amount of chilliness 

 produced in the air. 



The general state of the weather during any week can thus be 

 seen at a glance, as well as those elements which are considered to 

 have most effect on vegetation. 



The lines at the top merely indicate the date to which each vertical 

 line refers, the upper line giving the day of the month, the lower 

 one that of the year. 



