THE PARISH OF HALIFAX. XIX. 



a greater difference, for the narrow valleys and cloughs are 

 sheltered, often wooded, and may be inclined to the south, and 

 so gain a distinct advantage by receiving the sun's rays at a less 

 inclination. On the other hand, the moors are exposed to the 

 full sweep of the wind, and their slope is almost horizontal. 

 There is, therefore, no cause for wonder that the vegetation in 

 Elland Park Wood, which combines a south aspect with a low 

 altitude, is always considerably in advance of that of other and 

 less favoured parts of the parish. But more than this, the 

 variation of five degrees is quite sufficient to produce an entire 

 transformation of the flora : the plants that can maintain a 

 footing at the higher elevations are not only much fewer in 

 number but are almost all different species from those at low 

 levels. A change of altitude affects both the mean temperature 

 and the flora much more rapidly than does a change of latitude. 

 Hence the parish possesses, thinly scattered on the highest 

 moors, a few plants, like Trientalis and Rubus Chamaemovus, 

 which the botanist will find in great profusion at low levels in 

 Norway. 



The rainfall is more variable, both from year to year and 

 place to place, but its chief characteristic is its high average, 



owing to the elevation of the parish. The 

 Rainfall. annual fall at Halifax exceeds that at Wake- 



field or Leeds by about ten inches, but is less, 

 by fifteen inches, than the fall on the high moorlands of the 

 parish. Combined with the nature of the soil, and the 

 relatively high humidity of the air, this leads to a prevalence of 

 moisture-loving plants in the flora, such as the sedges, ferns, 

 and mosses ; although it should not be overlooked that though 

 the moorland plants may be alomst water-logged for consider- 

 able periods of the year, they have in the summer to withstand a 

 much severer drought than other plants which are less exposed 

 to the sun and wind. The ease with which a moor is fired is 

 an obvious consequence and demonstration of this fact. 



The details in the table below, derived from the same 

 sources as the previous one, illustrate the distribution of the 

 rainfall throughout the year. The Well Head readings extend 

 over a period of forty-five years, a sufficient period to afford a 

 reliable average. From these it is clearly shown that the 

 spring months (February to May) are the driest, whilst the 

 rest show but little difference from each other, except October, 

 which is decidedly the wettest month of the year. 



