SILK-WORMS. 
43 
the temperature of their hot-houses by their senses 
alone, without the aid of the thermometer. Sci- 
ence and practice shew, that few things are more 
uncertain, and less founded. 
The exterior sensations, and the disposition of 
the body, are often in opposition to the evidence 
of the thermometer ; thus the moisture or dryness 
of the atmosphere, although the degrees of heat 
may be the same on the thermometer, cause us to 
experience 'sensations so different, that we might 
feel cooler on a summer’s day, the thermometer 
being at 82° with a cold north wind, than we 
felt the preceding day, when a moist south wind 
blew, although the thermometer should have been 
many degrees lower. Thermometers are therefore 
indispensable*. 
* lathe book published by Mr. Dandolo, in 1816, may be 
found the following- passage : “ The distance marked from 
ice to boiling- water in the common thermometer is too small ; 
the degrees are too close, which sometimes misleads. To avoid 
this, I have had thermometers made for the use of the hot- 
houses, with a longer scale ; the distance of one degree equal 
to that of ten degrees in the scale of the common thermome- 
ters. In this manner I have been enabled to divide each de- 
gree into five fractions, which may be easily distinguished 
even at some distance. And thus the slightest variations in 
the temperature of the hot-house may be perceived at once. 
These thermometers have a mark to shew the extreme point 
to which spirits of wine rise," which spirit must be coloured. 
I must add, that I had them made with spirits of wine, because 
those made with mercury were too expensive ; however, when 
executed by a clever workman, they are very exact." 
M. Bellani de Monza, who made these thermometers, hav- 
ing explained them to me, 1 communicated his description of 
