534 



NATURE 



[February 23, 191 1 



for scattered papers and lectures, but can find in the 

 volume before us a risumi of his inquiries, with some 

 additional information, as well as a list of works, 

 old and new, which deal with some or other of the 

 topics discussed in Dr. Laurie's pages. This list 

 occupies nearly fifty pages, and is comprehensive if 

 not precisely exhaustive. 



Of the fourteen chapters into which this handbook 

 is divided, not the least important is that which forms 

 the introduction, in which a sketch is drawn of the 

 interdependence of certain crafts, of the development 

 of the processes of painting, of the increase in the 

 number of available pigments, and of changes in the 

 workshop and studio. Then in six successive chapters 

 there are described Egyptian pigments and mediums, 

 and classical methods, such as wax-painting, egg-tem- 

 pera, and a kind of fresco-painting. The eighth 

 chapter deals with the later history of fresco-painting, 

 and then comes a series of discussions based on the 

 treatises of the monk Theophilus and on the "Book 

 of the Art," by Cennino Cennini. By means of 

 abundant quotation from these authorities and by 

 original comment. Dr. Laurie has certainly succeeded 

 in reproducing " the atmosphere " described in the 

 preface as that "in which these ancient works were 

 carried out." As our author never loses his hold on 

 modern science and modern practice, we commend his 

 appreciative sympathy with the naive descriptions and 

 utterances of the older writers and historians of art. 



" On the painting of illuminated manuscripts " is 

 the heading of the eleventh chapter. There are here 

 some indications of the pigments used in such wonder- 

 ful productions as the "Book of Kells," and the 

 "Lindisfarne Gospels," both of the seventh century. 

 For instance, we learn that "the Irish monks had 

 learned to extract the purple dye from a species of 

 murex found on the shores of the Irish Channel." 

 Besides Tyrian purple the early Irish illuminators 

 had at their command red lead, several ochres, a green 

 identical with malachite and several lakes. The ink 

 they used is supposed to have owed its blackness 

 entirely to carbon, but a close examination of the 

 writing in the " Lindisfarne Gospels," recently made 

 by the reviewer, indicates, by the presence of a multi- 

 tude of reddish-brown spots, the employment of a 

 gallo-tannate of iron, like that described by Theo- 

 philus. To the subject of lakes and other "adjective " 

 colours, as used in ancient practice and in mediaeval 

 days. Dr. Laurie devotes a chapter of twenty-five 

 pages; the employment of dj^ed cloths as sources of 

 ?ome pigments, as in the case of the red from kermes, 

 or Coccus ilicis, is described. 



The last two chapters in the book are mainly given 

 up to the study of questions connected with the origin 

 of oil-painting, the making and use of varnishes and 

 the preparation of pigments and of canvas-grounds 

 during the sixteenth and seventeenth centuries. Dr. 

 Laurie admits that he is unable to pronounce definite 

 judgments on all disputed points, but he has certainly 

 contributed valuable material for a solution of some 

 of the problems offered bv pictures supposed to have 

 been painted in oil during the fifteenth century. 



In the volume under review are included thirteen 

 illustrations, many of them in colour. They are not 

 NO. 2156, VOL. 85] 



merely pleasing enrichments of the text, but serve tin 

 purpose of throwing light upon certain descriptlvi 

 passages. 



On the whole, we may consider that the aim of the 

 author has been satisfactorily accomplished and that 

 he has given, within reasonable compass, a fair ac- 

 count. In English, of the varied information scattered 

 very widely in the literature of the art of painting. 



In a second edition the author must correct a few 

 slips. For example, the two great lunettes painted 

 by Lord Leighton in the Victoria and Albert Museum 

 are not in true fresco (p. 136), but in spirit-fresco, 

 an oleo-resinous vehicle containing wax. Again, Dr. 

 Laurie has misplaced (p. 334) the Christian names of 

 the brothers van Eyck. Revision is needed elsewhere 

 also, as In the recommendation to use terre verte in true 

 fresco-painting (p. 137) ; It has proved very treacherous 

 in this country. Then, too, the attribution to Mr. 

 James Ward of the "valuable suggestion, unknown 

 to the older painters, namely, the Introduction of 

 asbestos into the plaster to bind it together " (p. 138), 

 does not fit the circumstances. Mr. Ward In his 

 " Fresco Painting," published in 1909, does, it is true, 

 recommend this use of asbestos, but It had been so 

 employed long before, and Its adoption had been 

 urged nineteen years previously in a well-known tech- 

 nical manual. A. H. C. 



THE COLLOID STATE OF MATTER. 

 Kapillarchemie, Eine Darstellung der Chemie der 

 Kolloide und verwandter Gebiete. By Dr. Herbert 

 Freundlich. Pp. viii + 591. (Leipzig: Akademlsche 

 Verlagsgesellschaft m, b. H., 1909.) 



THE attention which has been directed during 

 recent years to the colloid state of matter has 

 led to the publication of a very considerable literature, 

 and the subject is rapidly becoming an important 

 section of physical chemistry. We therefore welcome 

 Dr. Freundlich 's book as perhaps the most complete 

 attempt to deal with the subject as a whole on the 

 lines of a definite hypothesis, and bring it into clear 

 mathematical relation to physics. 



The colloidal state is usually, and possibly always, 

 a two-phased condition, In which one finely-divided 

 substance is suspended In another, and ranges by 

 Imperceptible gradation from such suspensions as clay 

 in water or butter-fat in milk to true molecular solu- 

 tions which to our present means of examination are 

 absolutely homogeneous. In such systems the sur- 

 faces of contact between the two phases are of 

 enormous area, and the phenomena of surface-action 

 and especially of surface-tension have an importance 

 of quite a different order to that which they possess in 

 single phases. Dr. Freundlich, indeed. Is inclined to 

 consider them essential causes, not merely of the pecu- 

 liarities of colloid solution, but of adsorption, co- j 

 precipitation, and electric cataphoresis, which often I 

 bear the closest resemblance to ionic chemical 

 reactions. While, however, the influence of surface 

 or surface-action is the guiding hypothesis of Dr. 

 Freundlich 's work, we have been particularly struck 

 with the candid and truly scientific spirit in which he 

 admits its limitations, and states opposing views. 



