Cause of vital Action in Animals and Plants . 
73 
external air from which the gun recoils. If recoil were attempted to be explained 
simply upon action and reaction, by the intervention of a force separating two bo- 
dies, whose resistances were as their densities, then the recoil would prevent any 
certainty of striking the point or mark against which the cannon is directed ; 
contrary to the effect proved by firing from triangles, iVIr. Perkins’s experiments, 
and the practice of every sportsman. The recoil too takes place, whether the firing 
be with blank or ball cartridge ; if the recoil be greater with a ball, it arises merely 
from the resistance which this offers to the discharge, alloAving time for the more 
complete ignition of the gunpowder, and the generation of a greater force; hence 
also the effect of a rifled barrel, and the recoil of a foul gun. 
The sky-rocket illustrates also this theory of recoil. To increase the surface of the 
composition exposed to combustion, the rocket is bored conically, nearly to its entire 
depth ; the products of this combustion are met by the atmosphere as they rush 
from the neck of the rocket, and recoil from the resistance ; as the cone enlarges, 
the force increases, and accelerates the ascent of the rocket, poised and directed as 
it is by the rod. The difference between the effects of the rockets and the shot is, 
that in the former the force increases from the gradual, but increasing surface in 
combustion ; in the latter, the force is at once generated, and the aid to the force 
which separates the shot from the mandrel is greatest at first, and though gradu- 
ally lessening, always adds something to the force of the discharge, until the air 
within the calibre is equalized with the atmosphere. 
The lather of the late Sir Wm. Congreve tried some experiments with shot fir- 
ed from a mandrel ; but as he bored the mandrel into which the discharge was put, 
and did not put the magazine in the chamber of the shot, they failed. 
As the expense of trying experiments with Mr. Sieviere’s engines is too great for 
an individual to incur, the probability of its becoming a most destructive engine in 
warfare ought to recommend it to the serious attention of Government. The ad- 
vantages of the lightness of the mandrel and the unlimited weight of the projectile 
are immense. When the experiment was made with the 25-pound shot, an inva- 
lid watchman carried the cannon shot and ammunition upon his head to Primrose 
Hill, before breakfast ; and the safety of the engine to those employed in its use 
may be shown in the fact, that the shot which burst did no injury to the gunner ; 
and no mischief could happen, for if the shot burst without advancing from the 
mandrel, the fragments dispersed at right angles, and if with any projection, in 
lines resulting from the united forces, leaving the gunner in safety. The recoil of 
the mandrel is very small, and arises only at the moment of separation from the 
pressure of the gases, which, escaping from the calibre, presses upon the end of 
the mandrel with effect proportioned to its surface. 
Ill — Notice of the Theory of 'SI. Dutrochet on the immediate or prox- 
imate Cause of vital Action in Animals and Plants . 
[From No. IX. of the Gardener’s Magazine ] 
The name of Dutrochet is well known in the scientific world, as connected 
with anatomical and physiological researches. ( Gard . Mag. y vol. i. p. 76. and vol. 
ii. p. 254.) In the present work he is considered to have surpassed all his prede- 
cessors in illustrating the laws of vital motion in plants ; and, as far as we are able 
to form a decisive opinion on the subject, we think he has discovered the immediate 
cause of the ascent of the sap. The various phy tologists who have preceded Dutrochet, 
and especially those of the latter end of the last century, have afforded us a very cor- 
rect knowledge of the organs of plants ; but it seems to have been reserved for this 
philosopher, to have determined their use in a more precise manner than has hither- 
to been done. 
The organs by which the sap ascend*, 31. Dutrochet has demonstrated to be 
those simple tubes, utterly devoid of valves, and without any lateral intercommuni- 
cation, which are situated both in the soft and hard wood. They are the lymphatic 
tubes of Decandolle, the false tracheae of Mirbel, and the corpusculiferous tubes of our 
author. They are not found in the bark, nor in the pith ; and it is well known 
that the sap does not rise through these parts of the stem. 
