186 
was convenient, their seclusion from light, some flowers have 
been ke]>t a fortnight in perfection. 
187 Camphor. The mention of this gum in the above article 
reminds us that some further notice of it may not be unac- 
ceptable. This substance exists in rosemary, thyme, sage, lav- 
ender, anemone, and other plants, but the article of commerce 
is imported from Japan, Sumatra, and Borneo. That from the 
two latter islands is obtained from a large forest tree called 
Dryobalanus camphora, of Forster, in a concrete state, by split- 
ting its central or heart-wood to pieces. The Japan Camphor 
is from a species of laurel, the laurus camphora, which the na- 
tives cut into chips, and obtain the camphor in a crude state by 
distillation. It is further purified in this country and submitted 
to a sort of sublimation, with steam. Camphor is lighter than 
water, and a singular phenomenon has been observed relative 
to its floating on this fluid which may interest some of our rea- 
ders. If into a bason of clean water a few small light pieces 
be scraped from a lump of Camphor, they will instantly com- 
mence whirling round on the surface with great velocity, some 
describing circles, and others spinning on their own axis. This 
phenomenon has not, we believe, been satisfactorily accounted 
for. 
188 Greenhouse Plants. As many of our readers are inter- 
ested in the management of Greenhouse ])lants, and our chief 
desire is to be useful to all, some hints on the general manage- 
ment of a greenhouse may not be unacceptable. It should be 
first observed that “ Greenhouse Plant ” is an appellation of local 
import only, for it will be seen, as a matter of course, that 
plants which will require the greenhouse in one country will 
not do so in another, nor even in opposite parts of our own 
country, as may be instanced in the difference of treatment 
some require in the north of England and Devonshire. 
The principal part of these which we cultivate in the Green- 
house are such as are natives of New Holland, the Cape of 
Good Hope, some parts of China, INIexico, and various other 
countries situate between the tenth and fortieth degrees of lati- 
tude, both north and south of the equator. It has been already 
noticed that altitude, or the height which any part of a moun- 
tain rises above the level of the sea, has its temperature affected 
