Dr. Sirén has most carefully weighed the evidence concerning the rival claims of the two or three replicas of the _Virgin among the Rocks_, one of which is in London and the others in Paris and Copenhagen, and he conclusively establishes the authenticity of the one in the Louvre, Paris. That one, the famous _Vierge aux Rochers_, is by far the most satisfactory in composition, and the faces and figures of the children are much more beautiful than those of the others. The one in the National Gallery, London, is by Ambrogio Preda, who was a close imitator of Leonardo. The figures have nimbuses in that one, but not in Leonardo's. Dr. Sirén illustrates his argument with a large number of plates. With respect to _The Last Supper_ at Milan, it is satisfactory to learn that Professor Cavenaghi, who has just finished a long and extremely careful scientific examination of the work, has proved that it is far better preserved than was believed. It turns out that very little indeed has been repainted; the heads are quite untouched, and though greatly damaged and obscured in places, we really are able to look at the actual work of the master. This has been a great surprise to the artistic world. The third part of the book deals with Leonardo's personality, and several good portraits of him are given. It is to be regretted that there is not one surviving that was taken when he was young, for it is related of him that he was almost divinely beautiful. In his old age his countenance is very impressive. Dr. Sirén discusses the moot question of Leonardo's alleged visit to Oriental countries, and he throws the weight of his opinion in favor of the journey. Certainly it is difficult to see how Leonardo could have given such accurate descriptions unless he had been to the places and undergone certain experiences. There are many gaps in his life which are yet unfilled by reliable evidence. When one reflects upon the extraordinary character and knowledge of the great man it seems not unlikely that he spent some time in the East receiving instruction which it was impossible to get in Europe. The fourth part consists of a translation into Swedish of his _Treatise on Painting_, and it gives, as Dr. Sirén says: a glimpse of a section through a soul-life filled with all that is possible or thinkable for a human being, of observation of nature, of experience of the world, of search for truth, and passion for beauty. One lays the treatise down with the grateful and humble feeling that one has stood before one of the greatest of our race, has met his eye and heard him speak. We may learn almost more about him from this work and from his sketches than from his pictures, for as Dr. Sirén says: