526 



and elegant experiments, by which he demonstrated that the pro- 

 position laid down by Dr. Croune in 1683 regarding the expansion 

 of water by cold is really correct; and that the phenomena observed 

 do not depend, as Hooke and others had maintained, on changes 

 occurring in the capacity of the vessel ia which the experiment is 

 conducted. From these researches, Dr. Hope concluded that the 

 maximum density of water is at 39^° or 40° Fahr. ; a result con- 

 firmed by the more recent and very accurate experiments of Hall- 

 strdm, who estimates its point of greatest density at 39*39° Fahr. 

 This, his favourite subject, received a still further elucidation from 

 him at a later period of his life. In 1839 he read to the Royal 

 Society of Edinburgh a paper, in which he showed that this law held 

 true with regard to water only in its pure state ; and that when it 

 contains saline matters in solution, as in sea-water, it follows the 

 ordinary law of regularly progressive expansion by heat and con- 

 traction by cold. 



The last communication which Dr. Hope made to the chemical 

 world was in 1843, when he read two papers on the colouring mat- 

 ter of the Camellia japonica, Magnolia (jrandiflora^ and Chrysan- 

 themum leucanthemum. In these communications, he asserted the 

 existence of three new proximate organic bodies, to which he gave 

 the names of Camelline, Magnoline and Leucarithemine, but which 

 he did not obtain in a separate form. 



Dr. Hope's claims on the gratitude of the chemical world are not 

 to be estimated bj his merits as an observer. He seems, from the first, 

 to have resolved to devote himself rather to the business of teaching 

 than of research. He spared no pains to make his lectures attractive 

 to the student ; his style of writing was elegant and concise, and his 

 delivery easy but impressive. The great chari^i of his lectures, how- 

 ever, consisted in the elegant experiments with which he illustrated 

 them : these were so well-devised, so skilfully arranged and so neatly 

 performed, that a failure on his lecture-table was an occurrence 

 almost unknown. One other circumstance which contributed to his 

 success as a lecturer was the excellent health which he enjoyed. 

 During a period of nearly sixty years, in which he was engaged in 

 studying or teaching medicine and chemistry, he was not more than 

 six days in all prevented by illness from discharging his duties. He 

 retained his vigour and his faculties with little diminution till within 

 a short period of his death; but in 1843, finding himself unequal to 

 the duties of his class, he arranged with his colleague Dr. Traill to 

 deliver the lectures for him, and shortly after resigned the appoint- 

 ment into the hands of the patrons. 



Dr. Gregory was appointed to the vacant chair, and before he had 

 entered on its duties his veteran predecessor died at Edinburgh on 

 the 13th of June 1844, in the 78th year of his age. 



Captain Basil Hall, R.N., was one of the younger sons of the 

 late Sir James Hall of Dunglass. 



Sir James was himself a man of very active mind, and is well 

 known to all geologists for the experiments instituted by him in cor- 



