52. Twin freaks
Classified, there are about ten distinct types of the window-pane frost. Representatives of each and all types never appear at any given time upon one window; and strangely enough the designs are never precisely alike on any two panes of glass. Reduplications of any previous design are extremely rare, and would only occur when a multitude of identical conditions occur.
This is rather singular, when we consider the different factors which go to form the window-pane frost. Certain panes of glass vary in thickness and in surface topography, also in the arrangement of minute, invisible scratches, and the accumulation of dust particles which collect from day to day, all of which affect the arrangement and collection of the frost crystals. It has been observed that double windows and furnace-heated apartments are not favourable to frost formations; but in rooms which are allowed to cool off at night, and in rural dwelling houses which are not heated by steam or furnace the Frost Spirit loves to work, and decorates their windows with his choicest etchings.
53. An unusual design
54. A powdering of small flowers
The beautiful frost studies illustrating this chapter were photographed in northern Vermont, where the winters are long and the cold very intense; affording the very best opportunities possible for the development and study of the frost etchings. These studies are, of course, somewhat magnified, yet you will have no difficulty in recognising many familiar frost designs.
[No. 35] is a linear type, and of rather common occurrence, easily recognisable.