694 POPULAR SCIENCE MONTHLY. 



The second of Dr. Dana's published writings was issued in 

 1833, while he was on a visit to England. It was a clear exposi- 

 tion of the chemical changes occurring in the manufacture of 

 sulphuric acid. 



In the following year Dr. Dana became resident and consult- 

 ing chemist to the Merrimac Manufacturing Company at Lowell, 

 Mass., in which position he remained for the rest of his life — a 

 period of thirty-four years. The improvements which he intro- 

 duced into the processes carried on in the mills of this company 

 were many and important. Dr. Hayes gives an outline of these. 

 He undertook systematic researches on the action of the dung of 

 beeves — then used for removing the excess of mordant in print- 

 ing calicoes with madder — which resulted in the discovery that 

 crude phosphates in a bath with bran are a complete substitute 

 for the expensive and disgusting material before deemed indispens- 

 able. Arseniates, which are cheaper than phosphates, were after- 

 ward substituted for them on the suggestion of Mercer, and are 

 the world-wide reliance of print manufacturers at the present day. 



Of the same systematic character was his study of the chem- 

 ical changes involved in the process of bleaching cotton fabrics 

 preparatory to printing them. This inquiry resulted in his in- 

 venting a method which not only received high commendation as 

 scientific work but was universally adopted in practice. As most 

 of Dr. Dana's researches were made for the exclusive benefit of 

 the company with which he was connected, their results were not 

 always published promptly, and hence the abilities that might 

 have won a high meed of fame remained known to only a small 

 circle. His discoveries with respect to bleaching cotton, however, 

 were published in the Bulletin de la Societe Industrielle de Mul- 

 house in 1838. The principles therein established have led to the 

 American method of bleaching, of which Persez, in his Traite de 

 V Impression des Tissus, says that " it realizes the perfection of 

 chemical operations." 



The Merrimac Mills were at first run by water power alone, 

 but when the works were extended this was supplemented by the 

 use of steam. Dr. Dana was now called to the new field of engi- 

 neering, in addition to his other duties. His development of the 

 whole subject of the evaporative power of coal and the economical 

 disposition of the heat in steam and in water of condensation is a 

 masterly efiiort, embracing every detail, and was in advance of 

 any published results of the time. 



For several years before he became a resident of Lowell, Dr. 

 Dana was frequently called to that city as a consulting chemist. 

 He was also one of the chemists consulted by the water commis- 

 sioners of both Boston and New York prior to the introduction of 

 the Cochituate and Croton water respectively. 



