Retrospective Criticism. 375 



men ax'e unanimous in admitting its utility ; though Mr. Knight, as well as 

 some others, Lias cles' nated the practice as worse than useless, and has 

 endeavoured zo esta.^ :h a system which he deems to be without the diffi- 

 culties inseparable fr;:.Ai the bark bed, and as possessing, at the same time, 

 every requisite necessary for the culture of all tropical plants. To those men 

 who object to bottom h at, as being unnatural, I must take the liberty of observ- 

 ing, that, even in our own climate, abundant proofs might be adduced to show, 

 that bottom heat is often produced in the natural soil, particularly in the 

 months of August, Se: ;?mber, and October; and, in humid and low situations, 

 sometimes a month or two longer. This is, no doubt, occasioned from the 

 earth being strongly heated by the summer sun ; the rain which falls in August, 

 and the following months, serving as a conducting medium for the heat pre- 

 viously obtained as well as for what follows : yet, on trial, on the mornings at 

 that season of the year, the temperature of the earth will be found to exceed 

 that of the superincumbent atmosphere ; but so far is this from being injuri- 

 ous to vegetation, that even Mr, Knight himself must acknowledge the reverse 

 to be the fact, since during that period of the year the progress of vegetation is 

 much more rapid than at any other period. The Rev. R, H. Williamson of New- 

 castle on Tyns (see his paper in Vol. IV. p. 24.) seems to understand the 

 subject of bottom heat better than any one who has hitherto made any refer- 

 ence to it; and v/ith !::s opinion I perfectly coincide. Mr. Knight is a gentle- 

 man much devoted to scientific pursuits, and especially gardening ; and it is 

 to be deplored that he should so often descend to sully his pen with as- 

 persions on the characters of humble and unaspiring practical gardeners. 

 Whether the gardeners in the vicinity of Downton are of a character to 

 justify the insinuations wrcAe use of by Mr. Knight, I cannot tell; for, although 

 I lived not very far from the site of his experiments, I never found any real 

 gardeners willing to admit the superiority of his practice. One thing is evident: 

 the diversity of opinion existing between Mr. Knight and many gardeners, 

 who combine science -vith practice (such, for example, as Mr. Fish), will lead 

 to diligence and investigation on the part of the young aspirant. — George 

 M.'Leish. Ville parmi les CoUines, Jan. 1836. 



Destroying the White Scale on the Pine Apple, Sfc. (p. 160.) — I did not see 

 L. O. L.'s rejoinder to my reply on this subject till yesterday. Viewing the 

 discussion in its proper light, it perhaps only concerns those engaged in it, 

 and is of little or no importance to the public. It is certain that, as the only 

 object in view is, that pine plants may be freed from the white scale, the best 

 method is that which is the simplest, provided it be effectual ; and no gardener, 

 who finds that a few applications of soapsuds have the desired effect, will 

 ever think of resorting to the more tedious process recommended by me. I, 

 however, am far from being convinced, by the evidence L. O. L. has adduced, 

 that plants can be effectually cleaned in the way he describes ; for, if so, how 

 is it that the insects upon his friend's plants required killing twice, or, perhaps, 

 even ot'tener ? That such was the case, appears to me to be a legitimate in- 

 ference from the following words : — "In destroying the insects, I was obliged 

 to deviate a little from what ivas my practice ivhen you were luith nie.^'' If I 

 rightly understand this passage (and, unless the plants were doctored a few at 

 a time, no other meaning can be attached to it), it implies, that the plants 

 alluded to had required cleaning more than once ; and, if so, may they not 

 require cleaning again ? I have been assured by two persons (one of whom 

 made trial of Speechly's recipe, and the other of the steam of hot dung, in the 

 way described by Mr. Fish), that although, for a time, the plants experimented 

 upon were supposed to be quite clean, yet in the course of the next spring 

 the insects re-appeared in myriads. Should it happen, however, that the 

 plants either of Mr. Fish, or of L. O. L.'s friend, continue clean until next 

 autumn, 1 shall then be convinced that the white scale may be destroyed 

 without previous removal ; if, on the contrary, those plants are found not to 

 be clean, I have a right to expect that they will make their failure known. All 

 I require, or ever have required, is conclusive evidence ; and, surely, L. O. L. 



