ee 
256 
Proceedings of Learned Societies. 
[April ty 
and growth. The roots of trees, par- individuals longest retain their health 
ticularly those in coppices, which are- 
felled at stated periods, continue so long 
to produce and feed a succession of 
branches, that no experiments were re- 
quired to prove, that it is not any defec- 
tive action of the root which occasions 
the debility and diseases of old varieties 
of the apple and pear-tree. Mr, Knight 
next details a variety of experiments 
which he has made to ascertain the fact 
he is anxious to establish; and having 
formerly adduced arguments which are 
uncontradicted, to shew that the sap of 
plants circulates through their leaves as 
the blood of animals circulates through 
their lungs; and having also shewn that 
grafted trees, of old and debilitated va- 
tieties of fruit, became most diseased in 
zich soils, and when grafted on stocks of 
the most vigorous growth, which led him 
to suspect that in such cases more fvod, 
is collected and carried up into the 
plant than its leaves can prepare and 
assimilate; and that the matter thus col- 
Jected, which would have promoted the 
health and growth in a vigorous variety, 
accumulates and generates disease in the 
extremities of the branches and annual 
shoots, while the lower part of the 
trunk and roots remain generally free 
from any apparent disease. Hence he 
attributes the diseases and debility of 
eld age in trees to an inability to pro- 
duce Jeaves which can efficiently ex- 
ecute their natural office, and to some 
consequent imperfection in the circu- 
lating fluid. It is said, that the leaves 
are annually reproduced, and are there- 
fore annually new; but there seems to be 
an essential difference between the new 
Jeaves of an old and of a young variety ; 
and it is certain, that the external cha- 
racter of the leaf of the same variety at 
&wo, and at twenty years old, is very dis- 
similar; and therefore to Mr. Knight it 
appears not improbable, that further 
changes will have taken place at the end 
of two centuries. ‘If (says he) these 
opinions be well-founded, and the leaves 
of trees be analogous to the lungs of 
animals, is it improbable that the natural 
debility of old age.of trees and of ani- 
mals, may originate from a_ similar 
source? This question Mr. Knight is 
not prepared to decide; but he believes 
at will be generally admitted, that the 
human subject is best formed for long 
life, when the chest is best formed to 
permit the lungs to moye with the most 
freedom. And he has long observed 
among domesticated animals, that those 
od 
and strength, and best bear excessive 
Jabour and insufficient food, in which the 
chest is most deep and capacious, pro- 
portionately to the length of current the ~ 
circulating fluid has to run; and the same 
remark he suspects will be found gene- 
rally applicable to the human species. 
Mr. Macartney has communicated to 
this learned body some very interesting 
observations upon luminous animals: he 
examines the grounds on which the pro= 
perty of shewing light has been ascribed 
to certain animals, that either do not 
possess it, or in which its existence is 
questionable, ‘He then gives an account 
of some luminous species, either inac- 
curately described, or quite unknown: he 
next explains, either from his own ob- 
servations, or from the information coms 
municated to him by others, many of the 
circumstances attending the luminous 
appearances of the sea: and he :hen de 
scrihes the organs employed for the pro- 
duction of light in certain species; and 
lastly, he reviews the opinions which 
have been entertained respecting the 
nature and origin of animal light. 
Mr. Macartney controverts the notions 
of many authors, who pretend to have 
witnessed tlhe phenomena of light as be- 
longing to animals, to which they cer- 
tainly, he thinks, cannot belong. Flau- 
gergucs pretended to have seen earth 
worms Juminous in three instances; the 
body shone in every part, but most bril- 
liantly at the genital organs. Now Mr. 
Macartney thinks it next to impossible, 
that animals so frequently before our 
eyes as the common earth-worm, should 
be endowed with so remarkable a pro- 
perty, without every person having ob- 
served it. If they only enjoyed it during 
the moment of copulation, still it could 
not have escaped notice, as these crea- 
tures are usually found joined together 
in the most frequented paths in the gar- 
den-walks, Inthe same way he treats 
many others; and then mentions some 
luminous animals discovered by Sir Jo- 
seph Banks, Captain ILlorsburg, and him- 
self: and he says, the zoophyte is the, 
most splendid of the luminous inha- 
bitants of the ocean. The flashes of light 
emitted during its contractions are so 
vivid as to affect the sight of the spec- 
tator, The luminous state of the sea 
between the tropics is generally accom- 
panied with the appearance of a great 
number of marine animals, of various 
kinds, upon the surface of the water. In 
the Arabian’ Sea have been geen severak 
luminous 
