346 On making Tea. 
do not admit an obvious explanation, and thus neglect 
many interesting phenomena, observed by mankind at 
large, whose experiments ought to be the best, being di- 
rected by no favourite theories, and biassed by no hypotheses. 
This idea is illustrated in many circumstances of daily oc- 
currence, and among others in the directions nsually given 
for the ordinary process of making tea; some of which co- 
incide with Professor Leslie’s experiments, while others 
seem hitherto to have received no explanation. It has been 
long observed, that the infusion made in silver is stronger 
than that which is produced in black earthen-ware, This 
remark is confirmed on the principles of the Professor, who 
has shown that polished surfaces will retain heat better than 
dark rough surfaces, and that consequently the caloric be- 
ing confined in the former case must act more powerfully 
than in the latter. It is further remarked, that the silver 
when filled a second time, produces worse tea than the 
crockery-ware ; and that it is advisable to use the earthen- 
ware, unless a silver vessel can be procured sufficiently 
large to contain at once all that may be required, These 
facts are readily explained, by considering that the action 
of heat retained in the silver vessel, so far exhausts the 
herb, as to Jeave little flavour for a second dilution; whereas 
the reduced temperature of the water in the earthen-ware, 
by extracting only a small portion at first, leaves some for 
the action of subsequent dilutions. The next observation 
we might at first view be ready to consider as a vulgar 
error, did it not admit an explanation on mathematical 
principles. It is supposed that the infusion is stronger m 
a globular vessel than in one of a different form ; and this 
must be the case, since it has frequently been demonstrated, 
that a sphere contains a given measure under less surface 
than any other solid ; from which it follows, that where 
there are two vessels of equal capacity, one globular and 
the other square, oblong, elliptical, or even cylindric, the 
spherical vessel having less surface than any of the other 
forms must throw off less heat; and that, consequently, the 
effect will be greater in the former case than in the latter. 
Tt is further observable, that the effect increases very ra- 
pidly, as the vessel is made larger, since the capacity in- 
creases as the cube, while the surface only increases as the 
square of the diameter. 
‘The reason for pouring boiling water into the vessel, be-' 
fore the infusion of the tea, is, that, being previously warm, 
it may abstract less heat from the mixture, and thus admit 
a more powerful action. Neither is it difficult to explain 
why 
