108 PROCESS OF MANUFACTURE. 
A standard thermometer, the bulb of which is continually 
kept immersed in the boiling syrup, indicates its density, 
and it is by far the simplest and most unerring guide that 
the sugar boiler can use for this purpose. When sugar is 
to be produced, the strike should be made at about 232° 
Fahr. (111° Cent.), but for syrup 228° Fahr. (109° Cent.) 
is the proper point. By the careful use of this instrument 
successive batches of the syrup may be brought to the 
proper poiat of concentration with perfect uniformity. 
There are some other simple tests of the density of 
boiling syrups which experience has proved to be reliable, 
and with which every practical sugar boiler should be 
acquainted. They are convenient at all times in confirm- 
ing the indications of the thermometer, and in the case of 
the accidental breakage of the instrument a knowledge of 
them would be almost indispensable. 
The first or lowest degrees of concentration beyond the 
condition of a very thin syrup are indicated by the appear- 
ances that it presents in falling from the thin edge of a 
skimmer or dipper upon which it has been taken up and 
exposed to the air for a few moments by turning it aboat. 
First, it falls slowly in large drops; then when the con- 
centration is further advanced it separates from the edge 
of the skimmer in broad thin sheets. Beyond this point 
the finger test or proof by the touch is regarded as the 
most accurate. The following account of it is given by 
Prof. R. S. McCulloh (“Scientific Investigations in rela- 
tion to Sugar and Hydrometers,” p. 272). 
“The proof by the touch is used, I believe, alike by the 
refiners and sugar makers of all nations, both in Europe 
and America, with very slight modifications. A small 
portion of the syrup is taken for trial between the index 
finger and the thumb; when it is cool, the finger is sepa- 
rated from contact with the thumb, and the syrup exam- 
