SCIENTIFIC SUMMARY. 
233 
very ingenious contrivance for this purpose. A vessel, containing air, is 
counterbalanced by a barometer tube, by inetins of a string passing over a 
pulley. The ends of each dip into two vessels contaming mercury, in which 
the surfaces are at the same level. The instrument will not be affected by 
changes of atmospheric pressure, but any changes of temperature will change 
the volume of the air in the vessel and cause it to rise or fall. 
BOTANY. 
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A New Irish Plant. — It is known to botanists that the flora of Ireland is 
in many ways peculiar, and more especially in relation to the circumstance 
that certain of the plants it includes are not only absent from this country, 
but are found in various portions of the Continent. Dr. D. Moore now adds 
another to the number of Continental plants found in Ireland. The new 
addition is Potamogeton nitens, one of the aquatic monocotyledons. It seems 
to hold a place between P. heterophyllus and P. prcelongus, but it may be 
distinguished from the former by its broader lower leaves, half embracing at 
the base, chaunelled and reflexed, its x^eduncle denser and shorter, its 
inflorescence and the absence (in July and September) of floating coriaceous 
leaves. From the latter it is known by its shorter leaves not hooded at the 
point, and lengthening into a foot-stalk at the base. P. nitens was discovered 
in considerable quantity in a large lake at a short distance from the sea, near 
Brandon Mountain, co. Kerry. In the beginning of last July it was scarcely 
in flower, and about the middle of September specimens collected presented 
the fruit in a condition of immaturity, yet ready to drop from the parent 
plant. — Vide Journal of Botany, No. XXIII. 
The Canadian Flora. — In a paper upon this subject. Dr. George Lawson 
describes the divisions of what he terms the floral carpet of North America. 
In some districts the vegetation is more developed than in others. Thus in 
the northern portions of Canada there are distinct indications of a thinning of 
this carpet. In the south-western peninsula of Canada there is a luxurious 
vegetation, composed largely of species which have their head-quarters 
farther south, in the adjoining states. In this locality there are magniflcent 
tulip trees, and black walnuts, the occidental plane, and such little southern 
plants as Jeffersonia diphylla, Azolla Garoliniana, and Erigenia hulbosa. 
This is the peach country of Canada, and the part peculiarly adapted for the, 
grape-vine, tobacco (now extensively cultivated), and Indian corn, all of which 
require in Canadian latitudes a maximum of summer heat. Gooseberries do 
not thrive, and although the soil is peculiarly adapted for turnip culture, the 
climate is too warm and dry. In like manner oats, broad beans, and cab- 
bages give way before wheat, kidney-beans, and pumpkins, all of which enter 
largely into fleld culture. In the south-western peninsula of Canada there 
are other plants that have a rather wider range northward and eastward ; 
such are Lupinus ■ perennis, Ranunculus rhomhoidens, Castilleja coccinea, 
Asplenium rhizophyllum, Woodwardia, etc. Viola sagittata is common 
about Toronto, but rather a local than a southern or western plant, and 
Podophyllum peltatum extends sparingly to Lower Canada. The prevailing 
and characteristic trees of Upper Canada are the beech, maples, several 
