Thomas Henry. 109 



name Malbon. He attended anatomical lectures, refused 

 a partnership which would have demanded seven years of 

 study for full medical practice, and returned to Manchester 

 as an apothecary, practising in the manner usual at the 

 time. This was a little before Dr. Percival's arrival. 



The paper read to the Royal College of Physicians on 

 * An Improved Method of preparing Magnesia Alba ' is the 

 first mentioned in the life by his son. It was written purely 

 with scientific interest, and the magnesia as medicine was 

 not prepared for sale until Mr. Henry had been strongly 

 advised, and had received the opinions of Sir John Pringle, 

 Sir Clifton Wintringham, Dr. Warren, and others. This 

 and some other essays were published in a separate volume. 

 Mr. Henry was elected a Fellow of the Royal Society, by 

 the interest of Sir John Pringle, Priestley, and Dr. Franklin, 

 and gradually rose into fame, whilst the family wealth 

 was solidly founded. Mr. Henry introduced to the English 

 chemists the works of Lavoisier up to the year 1776, and 

 illustrated them with notes. 



He also first observed that a certain amount of carbonic 

 acid in the air is favourable to the growth of plants, and 

 these experiments were received by Priestley with great 

 interest. 



His mode of keeping water pure at sea was an improve- 

 ment on that of Dr. Alston, of Edinburgh. Dr. Alston 

 had proposed the use of lime to prevent putrefaction, and 

 when the water was required he proposed to precipitate the 

 lime with carbonate of magnesia. This certainly unpracti- 

 cal proposal was changed by Henry into passing carbonic 

 acid though the lime-water and precipitating carbonate of 

 lime. This is the origin probably of Clark's process of 

 purifying water, and it is remarkable that such a simple 



