21 
49 Specific Gravity of Hot and Cold Water. The follow- 
ing experiment, from Dr. Lartlner’s Cyclopaedia, vol. 17, will 
elucidate some of the facts which we have previously stated, 
with respect to the transmission of heat by Water. If a quan- 
tity of cold water be thrown into a vessel, a thermometer being 
immersed in it, and a quantity of hot water be poured care- 
fully over it, so as to prevent the fluids mixing by the agita- 
tion, it will be found that the hot water will float on the cold. 
The thermometer immersed in the cold water will not rise; nor 
w ill a thermometer immersed in the hot water, poured over it, fall. 
But if, by introducing a spoon into the vessel, and agitating 
the water, a mixture of hot and cold be produced, the lower 
thermometer will immediately rise and the upper fall, and both 
will ultimately stand at the same temperature, intermediately 
between their former indications. If, on the contrary, hot wa- 
ter be first poured into a vessel, a thermometer being immersed 
in it; and then cold water be carefully poured upon the hot, so 
as to prevent such agitation as would cause the fluids to mix, 
and a thermometer be also immersed in it, it will be immediate- 
ly found that the lower temperature will fall, and the higher one 
will rise. In fact, the cold water descends through the hot by 
its superior gravity; but in this case the fluids, in passing 
through one another, become mixed, and the whole mass will 
take an intermediate temperature. 
50 Preserved Flowers and Plants. Mr. Lindsey, the intelli- 
gent manager of the Gardens at Chiswick House, has just pre- 
sented to the 3Iedico-Botanical Society some very beautiful 
and highly preserved specimens of dried plants and herbs, re- 
taining, in a peculiar degree, the whole of the volatile oil and 
aroma, and the colour of the recent plant. The plan adopted, 
is to dry the substance in a close and dark room; and not, as is 
usually the case, by exposure to a current of air and the action 
of the light. AVhen the separation of the aqueous particles is 
effected by their evaporation, and they are tolerably dry, they 
are submitted to pressure in small quantities, enveloped in pa- 
per, until the oil appears on the surface, and which is known by 
its discoloration; by this, all change of colour, by the action of 
the light, or further loss of volatile matters by evaporation, is 
prevented. In pot-herbs, as well as medicinal plants, the im- 
provement and superiority is very decided. 
112 60, New Mo. Mag. 
