What Leonardo painted and carved constitutes only a small part of his creative activity, a fragment of that great soul's universality.... Many of his designed works never reached expression ... others were left half done, and those which were carried out, have, moreover, in no small degree, had the misfortune to be destroyed or corroded and defaced by time. Many of Leonardo's most important works which are spoken of by the old writers, seem to have disappeared without leaving a trace. The great work of his prime, _The Last Supper_, is little more than a shadow of what it once was, and the powerful monumental composition of his old age, _The Battle of the Standard_, was only carried out in paint to a partial degree, and now can only be studied through imperfect copies. The stately equestrian statues which truly denoted the culminating point of that branch of art did not reach final material expression either, and only live in rough sketches and sundry imitations, while of the noble architectural projects for domed cathedrals, for mausoleums and palaces, for entire towns, not even one has come to anything.... The art historian has to trust to preparatory studies, to copies or imitations, to reports, in order to get an idea of the appearance and quality of the works of the master.... For analysis we have to lean on sketches when the finished work fails us. It cannot indeed be denied that herein lies a deplorable limitation and a special difficulty in the way of popularizing his work, but perhaps the limitation is not so great as many are inclined to assume. A great musical composer's preludes and fantasias may contain the beautiful motives of the entire symphony, even if the instrumentation is incomplete and the execution imperfect.... Leonardo has been placed before us as an ideal man, because his life and work are stamped by a sovereign balance which in our time is so greatly coveted and so rarely obtained. To the degree that the author has succeeded in letting Leonardo express himself, free from all fanciful embellishments and arbitrary hypotheses--speaking to the reader through his own words and art--he will consider his mission fulfilled and his work to possess something more than temporary value. There is no doubt that Dr. Sirén has done this and more than this, and we must heartily congratulate him upon the production of a most valuable contribution to the literature of art. It may interest our readers to know that engrossed as he is in his labors for the cause of the higher intellectual education, Dr. Sirén is able to find time to work strenuously for the Universal Brotherhood and Theosophical Society of which he is a very active member.