TRANSACTIONS OF THE SECTIONS. 259 



Fahrenheit, — a wet-bulb thermometer indicating at the same time 76° to 96°, or 

 always 4° less than the dry-bulb thermometer. In this arrangement 50 pieces of 

 25 yards are exposed at one time, and as each piece is a quarter of an hour under 

 the influence of the steam, 200 pieces pass through in an hour. 



The mordant, having thus received the requisite quantity of moisture, must be 

 left one or two days in an atmosphere still warm and moist ; and in some cases it 

 is advantageous to pass the goods a second time through the rollers. 



It had fortunately been ascertained long before, at Thornliebank, that exposure in 

 single folds after moistening was not necessary. Mr. Graham's experiments on the 

 diffusion of gases through small apertures had served to suggest that, for the ab- 

 sorption of the small quantity of oxygen required, the goods might as well be 

 wrapped up and laid in loose heaps. Accordingly, in the operation in question, the 

 moistened goods are carried in bundles into the building on the opposite side of the 

 midwall already mentioned, and deposited upon the sparred floors, which are placed 

 there at heights corresponding with the stages in the first apartment, on which the 

 goods are folded down. Upon these floors five or six thousand pieces, of twenty-five 

 yards long, can be stored at a time. It is necessary, of course, that an elevated 

 temperature, and a corresponding degree of moisture, be preserved in the storing 

 apartments day and night ; and 80° Fahr. is sufficient, with the wet bulb at 76°. 



The process of ageing, as thus detailed, was in operation at Thornliebank in the 

 autumn of 1856. About a year afterwards it began to be adopted by other printers, 

 and now (in September 1859) it is already in use at least sixteen different printing 

 establishments in Scotland and in Lancashire. 



On the Molecular Movements of Fluids. 

 By Thomas Graham, M.A., D.C.L., Master of the Mint, F.R.S. 



On a Symmetrical Arrangement of Oxides and Salts on a Common Type. 



By Dr. Lyon Playfair. 

 Salts, according to the present views, may be constituted of an oxide and an acid; 

 of an electro-positive element and an electro-negative salt radical ; or on the type 

 of water in which the hydrogen is sometimes replaced by an electro-positive element, 

 sometimes by an electro-negative compound. The author adopted the whole series 

 of metallic oxides as typical of salts, supposing that two equivalents of the metal 

 were present in all the oxides except the magnetic oxide. He contended that neutral 

 salts are not formed on the type of a basic oxide, such as water, but on that of a 

 neutral oxide, such as peroxide of manganese or peroxide of hydrogen, of the general 

 formula 2 (MM)O a . Two equivalents of the oxygen in this type may be replaced 

 in a neutral salt by an anhydrous acid, so that the general formula of a neutral salt 

 is either 2 (MM)A„, or hal'f that value, in which A represents any acid. The author 

 showed that many facts supported the idea that an anhydrous acid could substitute 

 oxygen directly, and vice versa. Thus, carbonate of manganese heated in air becomes 

 peroxide, oxygen substituting the acid ; while peroxide of copper loses oxygen in air 

 and becomes a carbonate. Barytes heated in air absorbs oxygen and becomes a 

 peroxide ; heated with sulphuric acid, it becomes a sulphate ; both oxide and salt 

 being formed on the same type. The author then proceeded to show that as there 

 are varieties of oxides, so also there are varieties of salts, each constituted on an 

 oxide type. Salts of suboxides represent the protoxides ; subsalts, with two equiva- 

 lents of an oxide and one of an acid, are formed on the type of sesquioxides ; while 

 those with three of a base and one of an acid, like phosphate of soda, are formed on 

 the type of magnetic oxide of iron. The sesquisalts, on this view, are on the type 

 of manganic acid, 0,(MM)A :1 , being like 0,(MM)0 3 . The author then proceeded to 

 show how various relations became apparent, if the oxygen in the oxides were 

 arranged in the simplest form, of an axis and equator around the metallic nucleus, 

 according to a conventional system, on a plane surface. The existence or deficiency 

 of symmetry in the structure of a body becomes thus indicated. As a general con- 

 clusion, when there is an equal balance in the molecules of oxygen, or of electro- 

 negative bodies playing its part, then rest or neutrality results ; when the structure 

 wants balance or symmetry, then activity is manifested— basicity when the electro- 



17* 



