V 



Wheatstone's stereoscope of two images of the human countenance, one 

 laughing and the other extremely serious, a normal state of countenance 

 would be produced. Accordingly he had two such pictures made of him- 

 self, and the effect which is produced by regarding the two images through 

 the stereoscope is so good, that his family and friends consider that it is 

 by far the best likeness which remains, and expresses most accurately his 

 natural condition of countenance. 



With but very shght knowledge of the use of figures, Mr. Appold 

 had very considerable power of mental calculation. He made curious and 

 extensive mental calculations which approximated very closely to the truth. 

 In this way he astonished Stephenson and other engineers by suddenly 

 stating how much he could by his own strength deflect the colossal bridge 

 over the Menai Straits. Upon accurate measurement it was found that 

 he really deflected it more than he stated, but then he said he used all his 

 strength, and had been afraid of overstating his case. His mode of calcu- 

 lating appeared to be by a geometric series, continually halving or doubling, 

 as the case required, from a known unit. 



During the last twenty years of his life he was always present when any 

 great engineering work was being carried out. He was ever watchful and 

 suggestive when difliculties arose, and contributed his share to the success 

 of the undertaking. In this manner he exercised an important influence, 

 and his loss will be keenly felt wherever new and diflicult mechanical 

 operations are attempted. 



We thus find that Mr. Appold was the author of inventions of great 

 originality in various departments of practical science. It is interest- 

 ing to know the manner in which he applied his mind for that purpose 

 It was his habit when a difliculty arose, carefully to consider the exac t 

 result he required, and having satisfied himself upon that point, he would 

 direct his attention to the simplest mode by which the end could be at- 

 tained. With that view he would during the day bring together in his mind 

 all the facts and principles relating to the case, and the solution of the problem 

 usually occurred to him in the early morning after sleep. If the matter 

 was difficult, he would be restless and uneasy during the night ; but after 

 repose, when the brain had recovered from fatigue, and when in the quiet 

 of the early morning no external influences distracted his attention, the 

 resultant of all known scientific principles bearing upon the question pre- 

 sented itself to his mind. 



Mr. Appold's inventions were essentially practical. They were not mere 

 proposals or paper inventions ; and he ever sliowed that he was a man of 

 action in bringing into successful operation his various designs. Great, 

 however, as were his powers of thoughtful invention he was not distinguished 

 in the study of the higher relations of the physical forces, and he left to 

 others the task of propounding those noble generalizations of modern days 

 which have done so much to simplify and dignify human knowledge j but 



