ONE PART PER MILLION 
How much is that? 
The expression "parts per million" (ppm) has 
moved from the laboratory into the columns of newspapers 
and magazines. DDT residues in soil, mercury in fish, 
herbicides in lakes and streams are all described in 
parts per million. The following examples reprinted 
in the newsletter of the Maritimes Forest Research 
Centre make it easier to visualize just how small a 
concentration is represented by the term. 
One inch in 16 miles is one part per million. 
A postage stamp is one part per million of the 
weight of an average adult. 
One gram needle in one ton haystack is one 
part per million. 
One part per million is a minute in two years. 
Your hand on the ground covers five parts per 
million of one acre. 
Every Ottawa naturalist needs: 
A GUIDE TO THE GEOLOGY 
OF THE OTTAWA DISTRICT 
by Alice Wilson 
A GUIDE TO THE GEOLOGY OF 
THE GATINEAU-LIEVRE DISTRICT 
by Donald D. Hogarth 
These indispensable booklets are available for 
$1.50 each, postpaid, from The Ottawa Field- 
Naturalists 1 Club, Box 3264, Postal Station C, 
Ottawa K1Y 4J5 
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