ANNIVERSARY ADDRESS OF THE PRESIDENT. XXXVll 



In 1852 he introduced the mode of propulsion with two or double 

 screws, now much adopted. 



The fine establishment for making muskets at Constantinople 

 was carried out by him, and he was constantly engaged in the con- 

 struction of a great variety of machinery, such as steam-engines on. 

 a large scale, dredging-machines, millworks, breweries, &c. &c. 



In 1850 he wrote a long report on the water-bearing properties 

 of the Bagshot district, for the purpose of supplying London with 

 water; in 1857 a paper to the Civil Engineers, on the history and 

 method of making beton or concrete ; in 1856, a report and project 

 for improving the entrance of the river Mersey, read at the Chel- 

 tenham meeting of the British Association. 



Besides actual works carried out, George Eennie was fond of making 

 physical experiments on the different subjects he had to consider, 

 the results of which he communicated to the societies of which he 

 was a member. His experiments on the strength of materials, three 

 years before those of IVCoria, are most accurate, and led the way to a 

 proper knowledge of the strain to which different bodies may be 

 safely subjected. They referred especially to the following sub- 

 jects : — On resistance of fluids, on that of soHd bodies in air and 

 water ; on friction ; on the expansion and contraction of iron and 

 stone arches ; on canal traction ; on the resistance of trains ; on 

 the development of heat by water in motion ; on the resistance 

 of screw propellers at different depths in the water. By these 

 and by many other experiments did George Eennie add to that 

 kind of knowledge which is as indispensable for the practical appli- 

 cations of engineering as it is important to general science. 



Endeared as he was to a large circle of friends by his unassuming 

 kindly spirit, no less than for his practical intelligence, a profound 

 feeling of sorrow was caused by the announcement of the serious 

 accident which, after many months' illness, terminated in his 

 death. 



Henry Darwin Eogers was born at Philadelphia in 1809, the 

 third of four brothers, who have all distinguished themselves in 

 physical science. At an early age he undertook professional duties 

 in Pennsylvania, and soon afterwards entered upon the long series 

 of elaborate surveys with which his name will remain associated. 

 It was especially in working at the great State-exploration of 

 Pennsylvania, in union with his brother, Prof. William Eogers, 

 who was charged with a similar task for Virginia, that his indus- 

 try and breadth of view were strongly manifested. The brothers 

 were supported by the aid of a numerous corps of assistants, and, 

 striding in the course of a few years over an area no less extensive 

 than full of interesting detail, were able, in 1842, to announce to a 

 meeting of the American Association of Geologists their conclusions 

 on the structure of the Appalachian chain, and this in a manner so 

 lucid and vigorous as not only to charm the hearers present, but to 

 rivet the attention of geologists in aU parts of the world. Those 

 who have enjoyed the advantage of hearing Prof. Eogers at a meet- 



