66 



ON THE MERITS OF IROK AND WOOD FOR ROOFS. 



than the severe frost on last Friday, Jan, 19th, when the ther- 

 mometer fell to 10 degrees below Zero, or 42 degrees of 

 frost. 



I am induced to send you this account of the degrees of frost 

 at Norwood, (which may be relied on), as I sat up the whole of 

 the night to make my observations and calculations, thinking it 

 might be interesting to some of your numerous readers 



Figure 1 , is the elevation of the front ; Figure 2, a transverse 



Fig. s 



