The methods of making the above determinations have been elaborated during the last twenty-five years to such an extent that they may be relied on for the purpose for which they are used, although they will, no doubt, be improved in the future, as they have been, from time to time, in the past. At present they are sufficient, not only as furnishing data which will form a satisfactory basis for arriving at the character of any bituminous material, but also as a means for control of the uniformity of any supply which may be selected, and for regulating its use in actual highway construction.
From what has been said it can be seen that the rôle of the chemist in highway construction to-day, where bituminous materials are becoming so important an element of it, is an important one, that science can contribute much to the improvement of highway construction, and that these contributions should not be neglected where it is proposed to do the highest type of work, and to produce a highway surface which shall resist the heavy travel to which they have been subjected since the advent of the motor car.
