A step has already been taken in another direction, that of furnishing special forms of instruments, better adapted to the uses to which they will hereafter be put, and purposely designed for chemical and analytical processes, for petrological pursuits, the geometrical measurement of crystals, for special work in connection with manufacturing industries, for the dairyman, and the farmer. For the detection of adulterations--that of butter, for example--a newer form of instrument has been devised, namely, a “Butro-refractometer,” by the help of which any adulteration of this universal article of diet will at once be revealed. The form of instrument upon which the optician has expended a greater amount of skill than perhaps on any other is the Bacteriological Microscope, as may be inferred from the larger space I have devoted to this important adjunct, since by original research, there can be no doubt a still greater future is in store for science in this special department of microscopy. But perfect success in this direction remains very much with the practical optician, and the further improvements made in the optical part of the instrument, since it is admitted that the highest theoretical perfection has not yet been reached.
It is a commonplace remark that every question solved is a step towards new problems waiting solution. It is equally obvious that many difficulties must be encountered by every author who uses his best endeavours to supply a standard volume or even a fairly comprehensive text-book on the Microscope, one that will remain a sure guide for any lengthened period. Such a success I regard as scarcely possible. I may, however, notice that my earlier work has met with a great amount of appreciation, and its utility acknowledged in the past by a demand almost unprecedented, edition after edition being called for.
It is hardly necessary to add that my task has been accomplished with an earnest desire to assist in diffusing a love for an instrument which has been my constant companion for upwards of sixty years.[1] Moreover, I have a firm conviction of the real utility of the Microscope in the work of education, its practical value in many branches of science, art, and manufacturing industries. These are my chief reasons for applying myself once more to the task of revision, rewriting, and rearranging and bringing this book as far as possible into line with the knowledge gained in chemical pathology and bacteriology.