38 



THE POPULAR SCIENCE MONTHLY 



were sometimes as large as the apples, and always had from 

 twelve to twenty perfectly shaped petals, from one inch to two 

 inches and three quarters long. 



It often happens that the clouds clear away and the tempera- 

 ture rises a few degrees while the direction of the wind is still 

 unchanged. Then the outer surfaces of the frost-forms become 

 glazed and the softer filling is blown out. They may be taken 

 off entire, and need no greater care in handling than fine china. 

 They are thin as eggshells and translucent, and under the micro- 

 scope show long rows of minute cells, separated by delicate fili- 

 form partitions. A contrary wind unclasps their hold and the 

 ground is strewn with the curious wreckage. They may be kept 

 for many days in a cold place. 



In sheltered places, a little way down on the leeward side of 

 the mountain, the deposits of frozen vapor are similar to the hoar- 

 frost seen in the lowlands, but greatly exaggerated in size and 

 profusion, and are usually in the form of small rosettes, set as 

 thickly as possible upon all surfaces of trees, rocks, or buildings. 

 The frost on the windows of all unoccupied rooms varies in 

 shape and amount according as the temperature is higher or lower. 



At fifteen degrees above zero, 

 small fern -shaped figures are 

 made, about a quarter or a half 

 an inch long. At lower tem- 

 peratures they decrease in size 

 and increase in numbers, until. 



Fig. 11. 



Fig. 12. 



at thirty degrees below zero, the panes are quite covered with tiny 

 frost ferns, twenty-five of which have been counted in a space an 

 inch square, every one perfect in outline. Above fifteen degrees 

 above zero the shape changes to something like the Hypnum 

 moss. 



Fig. 13 represents part of a pane. The temperature fell below 

 fifteen degrees for a short time, allowing the accumulation of a 

 few of the fern-forms, and then rose rapidly to twenty-five de- 

 grees, with the result here shown. The moisture condenses upon 

 the windows of inhabited rooms just about as it does everywhere 

 else. 



