3 6 THE POPULAR SCIENCE MONTHLY. 



ward and upward again from the ground, struck the one-story 

 wall D. 



Fig. 9 shows a section of the wall D in the beginning of that 

 storm. Unfortunately, the other negatives of that group were 

 spoiled. 



On C the deposits on cornice and weatherboards nearest D 

 partook of the shape and direction of those on D ; and the same 



FIG. 9. 



was true of those nearest B. In the space intervening, the frost 

 was laid on obliquely, resembling the first course of a heavy lat- 

 tice. All these walls, as well as all others on the mountain top 

 which faced the west and north, were completely covered, and 

 presented the appearance of exquisitely chiseled marble. 



On all flat surfaces, whether curved or rectilinear in outline, 

 when they are suspended vertically, faced to the wind, so that it 

 may blow past all sides unobstructed, the frost-forms lie at an 

 angle of thirty degrees to the surface, with their bases to its 

 edges, and point accurately toward the center. 



On a flat surface having a rim that projects as much as half 

 an inch, they are built on the inner edge of the rim, and extend 

 toward the center at a right angle to the rim and parallel to the 

 surface. When the rim is more shallow, their bases are set in 

 the angle where the rim joins the surface, and they stand out 

 from the surface at an angle of more than thirty degrees. 



Fig. 10 is the lid of a cream freezer, showing frost-forms point- 



