Betr aspect ive Criticism. 325 



As some of our readers may have forgotten our description of Perkins's 

 double boiler, we shall here repeat it from the Gardener's Magazine for 1832 : — 

 " Suppose we have a common boiler, such as is used in common wash-houses, 

 and in the siphon mode of circulating hot water ; then place another boiler 

 within it, of such a size as to leave only a few inches between the inner boiler 

 and the outer boiler all round, and support it in this position by stays, as shown 

 ■ in Jig. 43. : let this inner boiler have a hole in its 

 bottom, about one third of its diameter, and let its rim 

 be 2 in. below the level of the water to be heated. 

 These arrangements being made, and the heat applied 

 below, a circulation instantly takes place and con- 

 tinues ; the water coming into contact with the heated 

 bottom and sides of the outer boiler rising rapidly to 

 the surface and descending through the inner boiler, which thus necessarily 

 contains the coldevSt portion of the liquid." (Gard. Mag., vol.viii. p. 28.) 



Supposing Mr. Penn's mode of ventilating had no other advantages what- 

 ever than that of producing a feeling of comparative coolness in stoves, and 

 setting the fruit in forcing-houses, we should prefer it to all others on these 

 accounts alone. — Cond. 



Mr. Main^s Theory of Vegetable Develope77ient. — I feel gratified by the flat- 

 tering manner in which my essay was noticed by Mr. Main in p. 278. It 

 was necessary to take notice of his theory, because it had been brought 

 forward by Mr. Towers in support of his belief, that no greater vigour was to 

 be expected from varieties of the potato recently from the seed. I think Mr. 

 Towers's inference correct, that if all the parts of a plant are contained in the 

 original embryo, and if even the seed itself is only a further developement of 

 that embryo, then all that can ever be produced from a plant is created at its 

 first existence, and we have no grounds to expect benefit from seedlings; but 

 my experience in the greater vigour of varieties of other plants recently from 

 the seed; and seeing the infinite number of varieties and hybrids produced from 

 seed, have led me to adopt a different opinion. In our researches into the 

 operations of nature, when we fancy we have discovered a law or method by 

 which these operations are guided, we should promulgate it for the guidance 

 of ourselves and others; but, unless we can give demonstrative proof of our 

 opinion, it must still be subject to the inferences drawn from observation ; and 

 I hope Mr. Main will excuse me, when I say, I have not yet seen any de- 

 monstrative proof of the above theory. The subject of adventicity is involved 

 in mystery ; properly speaking, there can be no adventitious buds, nothing in 

 nature can be adventitious, all things are the work of infinite wisdom, which 

 cannot act by accident : but, when talking of the operations of infinite wisdom, 

 we are accustomed to call it nature ; and, when we see things take place in 

 a manner we have not been accustomed to perceive, we call it unnatural or 

 adventitious. And certainly, I think, when we perceive buds to spring in un- 

 common quantities, and from places where such quantities could not naturally 

 be expected from former experience, we are warranted in calling these 

 adventitious ; and to infer that, here, the theory of a normal quantity pre- 

 viously existing will not so well account for what we observe, as to confess 

 our ignorance of nature's method, and say the vital energy (a power whose 

 actions we cannot define) has organised these buds from the sap. To say they 

 were generated by the vegetable membrane or plate, is only transferring our 

 ignorance to these membranes, and causing them to perform actions which we 

 cannot define or demonstrate; these membranes are themselves organised from 

 the sap, if we are to believe other vegetable physiologists. To say, again, that 

 this vegetable plate or membrane, and all that may be generated from it, 

 originally existed in the embryo ; and that it contains innumerable buds and 

 other members which may never be developed, is a multum in parvo which is 

 nearly incomprehensible. And when we come to the doctrine of morphology, 

 and find that leaf buds may become flower buds ; that it needs only to shorten 

 an imaginary axis, and we have whorls of leaves converted into calyx, corolla, 

 stamens, and pistillum ; whether are we to believe that these existed in the 



