cxxx GENERAL SUMMARY OF SCIENTIFIC AND 



new light possesses many and decided advantages over coal- 

 gas ; especially will this be manifested in the score of econ- 

 omy, the cost of the electric light being, according to the in- 

 ventor's statement, about one fifth that of ordinary coal-gas. 



Before leaving the subject of illumination, it w^ould not be 

 amiss to call attention to the improvements made in the me- 

 chanical details of the gas-works, and especially in the numer- 

 ous endeavors whix;h have been made, with considerable show 

 of success, to introduce machinery for charging and draw- 

 ing the retorts. In this connection, the names of Somerville, 

 Rowland, and Havens are esj^ecially deserving of mention. 



In the preparation of chlorine, the most noticeable innova- 

 tion announced during the year just past is the new j^rocess 

 of Mr.Weldonjin which magnesia is employed along with the 

 manQ;anese. 



Within a short interval, quite a number of improved meth- 

 ods for this purpose have been made public, some of which 

 notably the first process of Mr. Weldon, those of Mr. Dea- 

 con, and of M. Tessie du Mothay have already come quite 

 extensively into use. 



For the sake of comparison, the accompanying brief de- 

 scription of these recent advances may be of interest; for al- 

 though, strictly speaking, only the one alluded to at the out- 

 set received its first announcement during the past year, they 

 have nearly all received more or less modification within 

 that period, and may be appropriately alluded to in the rec- 

 ord of progress for 18T3. 



The process of Du Mothay is designed to produce chlorine 

 continuously from a given supply of manganese. This is ef- 

 fected by passing a stream of hydrochloric-acid gas over a 

 mixture of the binoxide of manganese and lime heated to low 

 redness, and then, at the same temperature, passing a stream 

 of air over the residue in the retorts, by which the chlorine 

 in the manganese and calcium chlorides is liberated, and 

 passed with the first product into chambers for the prepara- 

 tion of bleaching lime. The revivification of the manganese 

 peroxide, the chief feature of the process, is eftected by the 

 presence of the atmosphere. There are no data at hand to 

 enable us to determine how complete this regenerating proc- 

 ess is found to be in practice. 



The process of Deacon consists in passing a mixture of hyr 



