116 



The Canadian Field-Naturalist. 



[Vol. XXXV. 



This slab, with its curved surface, may and 266 feet in length could in a period 



be considered _ to represent an arc of a f 75 ^.^^^,^ ^.. j^^^^ ^^ ^^^^^ -j^^^ ^ ^.-^.^l^ 



circle which, if completed, would have a .,.', , , ^ j.-, 



diameter of 85 feet. In other words, a '^ ^i^bjected to a stress no greater than its 



slab of Trenton limestone Wi inches thick own weight. 



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THE TREATMENT OF SKIN IRRITATIONS DUE TO POISON IVY. 



The excessive heat of last summer, caus- 

 ing profuse activities of the pores of the 

 skin, was to a measure responsible for the 

 large number of cutaneous inflammations 

 produced by poisou ivy. Persons who had 

 never before experienced the effects of 

 poison ivy succumbed to attacks this year, 

 and the usual feeling of security by per- 

 sons considering themselves "immune" 

 was largely lost. Observations for a period 

 cf years lead me to believe tha' no person 

 is permanently immune, unless he succeeds 

 ill' avoiding contact altogether. On the 

 contrary, people who heretofore were never 

 bothered by the effects of this plant, 

 and who claimed to be quite immune, be- 

 came violently affected when in a state of 

 profuse transpiration. 



The name poison ivy is well known 

 and scores of harmless plants are carefully 

 avoided by the camper or picnicker. It is 

 remarkable how few people do actually 

 know and recognize the plant. All ^ave 

 some idea, mainly the wrong one, until 

 they experience the effect on their own 



skin of having come into actual contact. 

 Where there is rocky ground or pure sand 

 beaches bordering woods, where pines and 

 ash grow, there is it necessary to survey 

 the ground for this bane of outdoor life. 

 Remember the three leaves of poison ivy, 

 whicli distinguis^i it readily from the five- 

 leaved Virginia creeper which it resembles. 

 In fall the leaves turn golden brown to 

 bright red and are not infrequently gath- 

 ered for their glory by the unsuspecting. 

 Beware ! Beyond the beauty lurks the beast, 

 and skin inflammations are sure to follow 

 indiscretion. One would expect that people 

 would be familiar with the appearance of 

 sudh irritation, but only those actually 

 affected remember the symptoms; indeed, 

 often enough poison ivy ras^ is not recc^- 

 nized by the learned professions. Invar- 

 iably children are the victims. Picking 

 berries, roaming among the brambles, their 

 naked feet covered with harmless minute 

 scratches ; their energy excites their spores 

 to increased activity and from a few 

 hours to a few days after, there appear the 



