124 ON IMPROVEMENTS IN MACHINERY AND APPARATUS 



whiten or destroy the greenish tint of the glass ; because in all cases in 

 which extraneous matters are used for the purpose, the glass so treated, 

 after continued exposure to light and to the action of the atmosphere, 

 rapidly becomes discoloured, and such productions obtain a bad charac- 

 ter. Purity of material, and great care in the chemical atomic propor- 

 tions of the matters used, should alone guide the manufacturer to a 

 good and useful glass. The Jurors would also caution the plate- glass 

 maker against using an excess of alkali, which he is tempted to do to 

 save time in fusing. Such glass readily " sweats ;" that is, the alkali 

 effloresces upon the surface of the glass, rendering it soon cloudy, and 

 requiring constant wiping. This description of glass is unsuited to 

 many purposes, and consequently obtains a reduced price in the market. 

 The specimens of crown glass, German sheet glass, both white and 

 coloured, as well as of bottles in every variety of metal, are all, most 

 creditable to the manufacturers who exhibit them. 



ON IMPROVEMENTS IN MACHINERY AND APPARATUS FOR 

 CLEANSING AND PURIFYING CASKS * 



BY ROBERT DAVISON, C.E. 



In the paper which the author had the honour of reading before this 

 Association in the year 1849, on the " Desiccating Process " he took 

 occasion to mention its application amongst others to the purifying of 

 brewers' casks, and further stated that upwards of one million casks had, 

 at that time, undergone the process. It was not, however, made 

 clear that the cask had to undergo a previous operation — namely, that 

 of cleansing — which was effected by machines of peculiar construction 

 which completely removed all adhering matter from the inside without 

 resorting to the expensive and injurious system of unheading. 



The object of the present paper is not only to confirm all that was 

 then stated as to the efficiency of the hot air system, by stating that 

 upwards of eleven millions of casks have since been treated in like 

 manner ; but to illustrate still further the importance of a proper 

 system of cleansing casks before any purifying process is applied. 



It may seem at first sight but an indifferent matter to bring before 

 an important Association like the present. But when it is considered 

 that there are no fewer than 2,400 public brewers in the United 

 Kingdom who brew something like 20,000,000 barrels of beer annually, 

 and assuming that at least an equal number of casks require to be 



* Read before the British Association. 



