An ordinary primed canvas was examined with the following results. The amount of moisture present was 5.5 per cent. of its weight, the priming 25 percent., and the dry substance of the size 15. The dry fibre which constituted the remaining constituent would weigh, therefore about 44* parts. It was further found, with the same canvas, in a dry heat of 100[degrees]C. (212 F.) continued for twenty minutes, that a strip 20 inches long became shorter by a quarter of an inch, changing in colour from a creamy white to a pale buff. After immersion in boiling water for twenty minutes a piece of this canvas 20 inches square was found to have shrunk rather more than 1 inch in one direction, and in the other direction rather more than half an inch. The piece was somewhat crinkled, and had become yellow in patches. ,,A few remarks as to the bearing of the above observations on some of the phenomena presented by oil-paintings on canvas may be here introduced. The water present in canvas varies with the temperature, and in consequence the dimensions of the canvas vary. As the contraction on drying+ and the expansion on taking up moisture are not the same in the direction of the warp as in that of the woof, there is an equal strain upon the layers of paint upon the surface. These may, therefore, become irregularly fissured, and even loosened. The importance of selecting a canvas so woven as to expand nearly equally in both directions is evident, but the maintenance of a uniform temperature, and of a suitable degree of moisture in the atmosphere where the pictures are hung, is also obvious. The absorption of moisture by canvas occurs through the back, unless that be also protected by paint. With the moisture deleterious gases may also be absorbed, and these may easily pass through and affect the priming, even the picture. Canvas protected by panel behind, or coated at the back with a layer of white lead which has been ground up with starch paste, escapes this injury in great measure, as the sulphuretted hydrogen, etc., are then intercepted. The colouring matter of the fibre and size of the canvas may move towards the front and discolour the the priming and even the picture. An excess of damp and a high temperature are the chief causes of this movement. When the first priming coat contains size, though it may adhere firmly to the sized canvas, it may not hold the subsequent oil-painting quite so tenaciously. Canvas is liable to accidental injuries from mechanical causes: a double canvas might mitigate the evil. The elasticity of the priming might not suffice,when the canvas is rolled up, to prevent cracking. A small addition of a non-drying oil, such as almond or olive oil, to the linseed oil used in the priming coats, proves useful, but such addition should not exceed 1 part non-drying oil to 20 of drying oil.