BERGERON-FINDEISEN DEMONSTRATED Although the Bergeron-Findeisen process is one of the most important theories of

meteorology, few of us will have seen it demonstrated in the laboratory. Even fewer can have witnessed the process in the real atmosphere.

I have been sent a photograph which suggests that one such witness is Jim Saxby, a Meteorological Office colleague, now retired to Canada (who will be remembered by some for the excellent in-house maths tutorials he gave to young hopefuls!).

The photograph is of a double-glazed window with an ill-fitting outer pane, taken in daylight from inside Mr Saxby’s flat in Oakville, Ontario. During a snowstorm of blizzard proportions, blown snow could be seen entering the chamber between the panes. There was originally a pattern of white frost on the inside surface of the outer pane. The blobs of ice grew quickly on this as the snow first melted on the inner pane (some water droplets can be seen), and then sublimed on to the frost. The outside temperature was -12°C and the room temperature 23°C. The largest isolated blob in the photograph is about 16 x 8cm. h e r Heath, Bucks.

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JACK SCoTT