170 THE HOT-HOUSE. [Feb. 



pour upon it one gallon of boiling water, which let stand till it be- 

 comes cold; then pour off the water for use. Repeat this on the 

 same quicksilver (for it will retain its powers) till a sufficient num- 

 ber of gallons are provided to fill a vessel intended for the purpose. 

 One in the form of a trough that will hold eight or ten gallons, is the 

 most convenient, especially for the large-sized plants. 



Then to every gallon of this mercurial water add six ounces of 

 soft green soap, dissolved in a portion of the prepared water. Let 

 the mixture stand till it becomes milk-ivarm, ivhich is the degree 

 of warmth it must be kept to during the time of dipping. 



Before I proceed to the method of applying the above mixture 

 to the plants, I cannot avoid calling in question, any virtue that 

 may be attributed to a mercurial efficacy therein; first, as it is the 

 opinion of the most experienced chemists, that crude mercury is 

 not soluble, in any degree in pure water, whether poured on in a 

 cold or boiling state; secondly, that if it contained any acid when 

 put on, which might decompose a part of the mercury, the adding 

 thereto of soap, would by virtue of its alkali, neutralize the acid, 

 and thereby disengage and precipitate the mercury: therefore, it is 

 at least very questionable, whether its efficacy is not exclusively 

 attributable to the alkali of the soap. 



If in place of the quicksilver or crude mercury above recom- 

 mended, you were to substitute corrosive sublimate, in the follow- 

 ing or even in a greater proportion, there is no doubt of its effectu- 

 ally answering the end, without doing the shadow of injury to the 

 plants. 



Dissolve half an ounce of corrosive sublimate in a pint of gin or 

 other spirits; ivhen dissolved incorporate thereivith four gallons of 

 soft water, and it ivill be ready for use. 



The soft soap may be added thereto, in the proportion above 

 mentioned, but its alkali acting on the acid of the sublimate, will 

 convert it into a mild muriate of mercury, and consequently render 

 it much less active than before. 



Previously let it be observed, that this dressing cannot be effectu- 

 ally applied with propriety to fruiting pines, either after they have 

 started their fruit, or for two months before it, as disturbing their 

 roots at that time would prevent their fruit growing to the full 

 size; however, succession plants may be dressed at any period, but 

 in the month of October that work can be done with the greatest 

 success; and fruiting plants, if infested, may at any time be washed 

 with the solution, which will destroy such insects as affect them 

 above ground. 



Before the plants are taken out of their pots, I would advise the 

 brushing oft' a few of the scaly insects (as in a common dressing) 

 especially towards the bottom of the leaves, where they will some- 

 times be so numerous as in appearance to lie one upon another, in 

 which case the mixture might be prevented from penetrating to 

 the bottom insects. I do not know that this business of brushing 

 is absolutely necessary; but as the whole operation in a large 

 hot-house may be performed in one day, the labour of a person or 



