1885. | Glacial Origin of Presque Isle, Lake Erie. 865 
is of considerable importance. That phase of the question, how- 
ever, pertaining to flowering plants has been elsewhere treated, 
It remains to speak of the sanitary relations of the new and addi- 
tional fact which has been established by the present experiments 
concerning odorous leaves as ozone-generators. Owing to the 
fact that few varieties which have markedly odorous leaves are 
cultivated within doors, their sanitary bearings may be regarded 
as being slight, the leaves of the geranium and other species 
usually seen in dwellings being feeble in their ozone-generating 
properties. Again, it should be remarked that when kept in- 
doors the odors given off both from the flower and foliage are 
sometimes not only objectionable to the senses, but also may 
prove detrimental, It is evident that such plants should be dis- 
carded, 
The case is widely different when we apply the results of our 
labors to the question of the hygienic value of out-door vegeta- 
tion, and more particularly of pine groves. Under these circum- 
stances unpleasant odors do not form a positive objection, whilst 
the species emitting the most pronounced odors are capable of 
rendering valuable hygienic service by furnishing ozone to the 
surrounding medium, Since the exhalations from the pine foliage 
are active agents in generating ozone, it follows that all of the 
important hygienic advantages of ozone are to be derived, to 
a marked degree, from the presence of pine woods.’ 
:0: 
GLACIAL ORIGIN OF PRESQUE ISLE, LAKE ERIE. 
‘BY T. DWIGHT INGERSOLL, 
HE peninsula of Presque isle is an extension of the main 
“ land opposite the city of Erie, Pennsylvania, reaching out 
into Lake Erie in a north-eastern direction. It is crescentic in 
form, the convex portion facing the lake with the shore line bend- 
ing toward the mainland, and forming Erie harbor, which is 
known also as Presque Isle bay. The. bay is about four miles in 
length by about two in breadth, with an entrance on the east. 
Government operations have made the bay somewhat historical, 
The vessels of Commodore Perry’s fleet were built here in 1813, 
1 For a fuller discussion of the subject of the sanitary relations of pine forests, see 
article by J. M. Anders, on “Sanitary Influence of Forest Growth,” a paper read 
before Phila, Go. Med. Society, Oct. 22, 1884. 
