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26 SORGHUM SUGAR INDUSTRY. These methods have been employed â¢with precautions adapted to the exigencies of the special problems for the solution of which the investi- gation has been instituted. By a judicious system of checks and con- trol, and by the reduction to the lowest limit of the personal error of the observer, the accuracy and constancy of the results have been as- sured as far as, in the present state of our knowledge, such end can well be attained. The care with which the methods for the determination of cane-sugar have been tested, aud the probable error determined, enlists our confi- dence. The reserve with which the Chemist has refrained from accept- ing the results as conclusive, until by repetition and variation in the methods he had exhausted the means at his command to prove them to be erroneous, is in the true spirit of scientific research. The analytical work prior to 1882 comprises the enormous number of nearly 4.500 analyses of forty varieties of sorghum and twelve varie- ties of maize, covering all the later stages of development of the grow- ing plant. The average results of these analyses, conspicuously dis- played in the form of graphical charts, afford a connected view of the progressive development of the juice through the various preliminary stages to and beyond the point of complete maturity. Such an amount of analytical work as is implied in the careful con- duct of nearly live thousand quantitative analyses, with a rather lim- ited number of assistants, and in an inconveniently arranged and con- tracted laboratory, was rendered possible only by the most rigid system and subdivision of labor in the workâa system in which each assistant was, for the time, devoted exclusively to one thing, e. g., determinations of density by the balance, volumetric determinations of glucose and sucrose, polarizations, ash determinations, total solids, ash analyses, analyses of the seed, quantitative determinations of acids and other proximate constituents of the juices at seventeen different stages of growth of the plant and after maturity. By this system each coworker became thoroughly expert as a specialist in his own duty; and it was thus possible by this system to test the accuracy of the work by sub- mitting identical samples in duplicate and separate numbers for analysis by the same and by different coworkersâa crucial test of verification. The Committee have critically examined the work done in this way, and for the details, showing a surprising agreement, refer to the appen- dix (p. 142). COMPARATIVE RESULT OF ANALYSIS AND POLARIZATION. The optical method of determination of sugar values, now commonly employed by sugar boilers, has found a wide term of comparison with the analytical results in the sorghum and maize sugar researches of the Department of Agriculture. The comparisons in 1879-1881, between large numbers of determin- ations by the cuprous precipitation and by polariscope appeared to sustain the opinion that there was a pretty constant difference in favor of the volumetric method, i. e., that the polariscope for some unknown reason failed to detect as much sugar as was demonstrated by the method of precipitation. These differences are set forth below, together with the very satisfactory results of over five hundred similar determinations made in 1882, from which it clearly appears that the discrepancy form- erly noticed is apparent and not real. This conclusion removes any doubt which hung over the practical value of the optical method; and this is practically of much moment, for in the rapid operations of the
