DYEING AND CALICO PRINTING. 319 



by this process alone, although as much so as if it had hung a whole day 

 in cold air. It has received, however, the requisite quantity of moisture 

 (about seven per cent, of the weight of the printed piece), and is thereby 

 enabled, if an iron mordant, to take oxygen from the air, and to become 

 changed (with time) into the sexquiacetate and sesquihydrate of iron. 

 In order to be sufficiently aged it must be left one or two, or even three 

 days in an atmosphere still warm and moist. 



" It had fortunately been ascertained long before, at Thoinliebank, 

 that exposure in single folds after moistening was not necessary. Air. 

 Graham's experiments on the diffusion of gases through small apertures 

 had served to suggest that for the -absorption of the small quantity of 

 oxygen required, the goods might as well be wrapped up and laid in 

 heaps. Accordingly in the operation in question, the moistened goods 

 are carried in bundles into the building on the opposite side of the mid 

 wall already mentioned, and deposited there on 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 seven 

 or eight thousand pieces may be laid at a time, and as each piece is 

 twenty -five yards long, 100 miles is therefore the quantity that can be 

 stored at once. It is necessary, of course, that an elevated temaerature, 

 and a corresponding degree of moisture be preserved in the storing de- 

 partments day and night, and 80 deg. of Fahrenheit is sufficient with the 

 wet -bulb at 76 deg. To effect that object a large iron pipe is placed 

 along the ground floor underneath, and moderately heated by steam, 

 while a row of small jets in the same position are made to project steam 

 directly into the air of the apartment. The whole building is defended 

 from external cold, and consequently from condensation of steam, by a 

 warmed entrance room, and by double windows and double roofs. 

 Small steam pipes are also placed at other points where they seem to be 

 required ; and the apartment with rollers is specially heated when not 

 in use, by a couple of* steam pipes, which are placed under the ceiling of 

 the ground floor. 



" The process of ageing, as thus detailed, was in operation at Thorn- 

 liebank in the autumn of 1856. About a year afterwards it began to 

 be adopted by other printers, and now it is already in use in at least 

 sixteen different printing extablishments in Scotland and Lancashire. " 



One of the greatest benefits which chemistry has conferred upon 

 manufactures is that of finding profitable employment for refuse mate- 

 rials. Thus it was for a long time considered that madder when re- 

 moved from the dyebecks was exhausted, or to use the technical term, 

 " spent." It was, however, discovered in 1843, by M. Schwartz, that 

 if this refuse was mixed with sulphuric acid, and heated for several 

 hours by steam, a considerable quantity of colouring matter was 

 liberated, and after the spent madder was well washed, and all trace of 

 acid removed, a product was obtained to which he gave the name of 



