JOHNSTON'S EXPERIMENTS. 13 



Dr. N. B. Ward, did much towards proving to students 

 of nature that the magnificent views of Priestley, 

 Daubeny, and others were both true and capable of 

 being practically applied. Mr. Ward, in 1842, pub- 

 lished a little work which gave a series of experiments 

 showing that animals and plants might be kept in air- 

 tight glass cases, and that each might be so adjusted 

 as to breathe in what the other breathed out. He had 

 commenced this study in 1837, and the celebrated 

 " Wardian cases " for 'ferns, now to be seen in most 

 drawing rooms, are the popular results. Dr. John- 

 ston, the well-known writer on ' British Zoophytes,' 

 adopted the above-mentioned compensatory principle 

 in 1842, at which time he had a store of sponges, 

 zoophytes, &c., in course of artificial preservation for 

 scientific purposes. These animals were kept in small 

 vessels wherein had been placed the common Coral- 

 Una, the sea lettuce (Ulva), and several others; and 

 the result was so successful that he suggested the 

 possibility of marine aquaria on a more extended 

 scale.* 



The knowledge thus gained by a few experiments 

 was destined shortly to receive considerable accre- 

 tions. In 1850, Mr. R. Warington (whose name is 

 inseparably associated with the history of aquaria) 

 made a communication to the Chemical Society on 



* The first attempt to keep the sea water constantly fresh by the 

 presence of living seaweeds was successfully carried out by Mrs. Anna 

 Thynne, in 1846. 



