384 A YEAR S WEATHEK. 



cannot escape, they are prisoners, but they thrive under their new- 

 conditions ; it is a case of mutual interdependence, the algae receive 

 mineral salts, iron, lime, potash, magnesia, and phosphorus, and 

 give to the lichens carbo-hydrates. This relationship is known as 

 symbiosis, and is a phase in plant life particularly interesting at 

 this season of the year when every exposed stone almost, and 

 every tree attests its success. 



The weather in February, 1 792. — one hundred years ago — was a 

 little colder than with us this year, there were more frosty nights, 

 but not so much snow. By the 8th, the thrushes were in song 

 and the primroses in flower, on the 12th the honeysuckle leaf was 

 out, and that of the gooseberry just ready to expand. The wind 

 went out on east as it has done this year. The rainfall was 2'20 

 inches. 



March 17th, 1892. 



MARCH. 

 The driest March for fifty years. The meteorological 

 aspect shows three distinct periods of dryness from the ist — 8th, 

 nth — 13th, 17th — 31st, leaving few days on which rain fell. On 

 one of these, the 15th, we had a gale and a downpour of over 

 half-an-inch of rain following a wet day, yet the whole rainfall for 

 the month was little over one inch — i'o7 inches. The last March 

 which was nearly as dry was in 1854, the rainfall being i"o8 inches- 

 Our average March rainfall at Truro is close upon 3 inches ; some 

 years we have twice that amount, but records of only one-third 

 the usual supply are very rare. We had wet on two mornings 

 only during the month and on three afternoons ; most of the rain 

 fell in the night. The sun was fully visible on 2^ days and seen 

 in gleam on 4 others, leaving 2 sunless days. The winds had a 

 tendency for north and north-east, giving a chilly feeling to the 

 air. On the 15th the wind veered westerly, and gained such force 

 that great damage was done to property and trees. We had frost 

 on 17 nights, the coldest in shade being 22 degrees — 10 degrees 

 of frost — an exposed thermometer registered on the nights of the 

 12th and 14th 16 degrees, or 16 degrees of frost. On one of these 

 nights we had hoar frost. We had hail on four days and snow 

 and sleet on two. 



The average coldness of nights for the month was ^^'^ degrees 

 the mean warmth in shade during the day for the month 47*4 



