with all the precautions known to science up to this point the utmost celerity is necessary to secure the best results.  There is here, however, a natural division in the process of sugar making, which will be further considered under the heading of “Auxiliary Factories.”  Any part of the process heretofore described may be learned in a few days by workmen of intelligence and observation who will give careful attention to their respective duties.

BOILING THE SIRUP TO GRAIN THE SUGAR.

This operation is the next in course, and is performed in what is known at the sugar factory as the strike pan, a large air tight iron vessel from which the air and vapor are almost exhausted by means of a suitable pump and condensing apparatus.  As is the case with the saccharine juices of other plants, the sugar from sorghum crystallizes best at medium temperature.

The process of boiling to grain may be described as follows:  A portion of the sirup is taken into the pan, and boiled rapidly in vacuo to the crystallizing density.  If in a sirup the molecules of sugar are brought sufficiently near to each other through concentration—­the removal of the dissolving liquid—­these molecules attract each other so strongly as to overcome the separating power of the solvent, and they unite to form crystals.  Sugar is much more soluble at high than at low temperatures, the heat acting in this as in almost all cases as a repulsive force among the molecules.  It is therefore necessary to maintain a high vacuum in order to boil at a low temperature, in boiling to grain.  When the proper density is reached the crystals sometimes fail to appear, and a fresh portion of cold sirup is allowed to enter the pan.  This must not be sufficient in amount to reduce the density of the contents of the pan below that at which crystallization may take place.  This cold sirup causes a sudden though slight reduction in temperature, which may so reduce the repulsive forces as to allow the attraction among the molecules to prevail, resulting in the inception of crystallization.  To discover this requires the keenest observation.  When beginning to form, the crystals are too minute to show either form or size, even when viewed through a strong magnifying glass.  There is to be seen simply a very delicate cloud.  The inexperienced observer would entirely overlook this cloud, his attention probably being directed to some curious globular and annular objects, which I have nowhere seen explained.  Very soon after the sample from the pan is placed upon glass for observation, the surface becomes cooled and somewhat hardened.  As the cooling proceeds below the surface, contraction ensues, and consequently a wrinkling of the surface, causing a shimmer of the light in a very attractive manner.  This, too, is likely to attract more attention than the delicate, thin cloud of crystals, and may be even confounded with the reflection and