which the painter can commit is the choice of colours which fade, or become discoloured in the course of time. Cornelius, when executing the frescoes in the Glyptothek, at Munich, met with several difficulties of this kind, and he was accused of not understanding fresco-painting. When I was called upon to report upon the case, I found that the plaster was rotten, and contained much sulphate of magnesia or bitter salt. I ordered this ground to be entirely removed, and to be replaced by a new one, prepared with washed sand and distilled water. No further complaint was made, and the paintings have stood very well. Much depends, also, upon the lime used in the mortar. If slaked and kept moist for some time, it answers better than freshly slaked lime; if poor it acts better than rich; lime containing magnesia, oxide of iron, or manganese, is better than pure lime.1

Encaustic painting has two enemies; the mortar ground and the organic materials used for painting, which are subjected to the natural laws of decay and decomposition.

In more southern countries, as in Italy, frescopaintings withstand, no doubt, longer the ravages of time than in northern climates; they are, however, not quite exempt from destruction, as is proved by Raffael's frescoes in the Loggie of the

1 The preceding remarks are very important to frescopainters.-W. C. T.

Vatican, which are said to have suffered considerably; and it has been found necessary to take precautions to prevent the further spreading of the destructive action.

In order to test the advantages of stereochromy, proof-plates were submitted to the roughest treatment; they were exposed for weeks to rain and frost; the ice which had formed upon them was allowed to thaw in a warm room, and this freezing and thawing process was repeated without in the slightest degree damaging the plates, whilst frescopaintings treated in the same manner became quite friable, and crumbled to pieces.

A small stereochromic picture was exposed on the roof of the Royal Museum at Berlin, near the chimney, to the action of wet and cold, smoke and soot, for a whole severe winter. When taken down in spring, it certainly looked as if it had been completely spoiled; but, upon being washed with spirits of wine, it was found to be as fresh as it ever had been. A small picture (two peacocks) on the west side of Herr von Kaulbach's atelier, close to the ground, has been preserved well, although the wall is thoroughly damp, and covered with shrubs in summer. It deserves to be noticed, that the damp and the efflorescence of the wall, during this rather long period of time, had scarcely any damaging effect upon the picture.

A further proof of the durability of stereochromic paintings will be found in the two pic

tures of the country house of M. Himbsel, on the Lake of Starnberg, to which I have already referred. They are now six years old, and are still as fresh and unchanged as if they had just come from the hand of the artist, in spite of storm and weather, which often sweeps from the west over the lake close by, and dashes the rain upon the walls with such force that it runs down in streams, forming sometimes crusts of ice in winter.

Stereochromy offers considerable advantages to the artist; painting is quite in his power, as well as the material, whilst fresco-painting makes him a slave of the latter. He is able to interrupt his work and continue it again after a shorter or longer time; he can retouch his painting before fixing it as often as he thinks it desirable. The finest colouring, the slightest touch of light and shade, the harmony of colours, and, consequently, the greatest perfection of a painting are in his power.

Stereochromy possesses that advantage which fresco-painting also has over oil-painting, that the colours are not shining, and that the observer can get a full view of a picture in whatever position he may be.

I have given a description of the principles upon which stereochromy is based, and I cannot help remarking, in conclusion, that this one investigation has cost me more time and labour,

together with considerable outlays and expenses, than most of my other investigations put together. Several of my friends could testify to the same; many of them assisted me materially in my difficulties, and I offer them my deep-felt gratitude at the conclusion of my labours. But, before all, I thank God, who graciously allowed His weak and aged servant to finish the preceding investigation of the water-glass, and its application, so far that others may build upon the foundation I have laid.

To the Giver of all good be thanks for all joys and sufferings experienced! May His blessing be upon the work!

Omnia ad majorem Dei honorem et gloriam ! Munich, Nov. 20th, 1855.

[A continuation of the various other applications of the water-glass will soon follow.]'

1 Death has put an end to the labours of the learned philosopher, and the reader will not see the promised continuation. Fuchs had a presentiment of his approaching death when he wrote the above concluding lines, and he, who never deceived others, and rarely himself, was not deceived in this presentiment. He died eighty-two years old, on the 5th of March, 1856. Two of his pupils and friends have shown what Fuchs did for his country and for science-Professor Dr. von Kobell, in a commemorative oration delivered on the 25th of March, 1856, the anniversary of the foundation of the Royal Bavarian Academy of Science; and Professor Dr. Kaiser, in a necrology, published in the March number of the Journal of the Society of Arts and Manufacture of the Kingdom of Bavaria.

DR. M. PETTENKOFER.

APPENDIX.

I.

Report by DANIEL MACLISE, Esq., R.A., on the "Water-Glass" or "Stereochrome" Method of Painting.1

BEING required to describe the method of Stereochromy, and to state my opinion of that process as adapted for mural or monumental painting, I attempt the fulfilment of this duty the more willingly, now that my daily practical experience confirms me in the belief that this process can supply to the artist a ready means for realizing some principal objects of his desire, which, hitherto, he could not equally attain even at the cost of much labour and anxiety. In order to explain by what conditions, and owing to what results, stereochromy is to be regarded as better fitted for the execution of mural painting than fresco, it will be necessary to bring here under comparison the leading features of both processes so as to estimate fully their respective merits, chemically as well as artistically.

My attention was directed to the new art of stereochromy, as successfully applied to mural decoration, at the time when, having completed my cartoon illustrative of the meeting of Wellington and Blucher on the field of Waterloo after the victory, I was about to engage in the task of reproducing the picture in fresco. In preparing to effect this, I became anxiously mindful of the many and various difficulties to be encountered, and these seemed almost sufficient to dissuade me from the undertaking. Of those difficulties, such as they are, the frescopainter of modern times is painfully aware, and so likewise

1 Vide Twelfth Report of the Commissioners on the Fine Arts.