696 THE POPULAR SCIENCE MONTHLY. 



As soon as Plateau found himself fairly out of the physicians' 

 hands, with restored health, he resumed his experiments with 

 ardor. He was most happy in finding co-laborers who gave him 

 the most efficient and willing help. " Thanks to their generous 

 co-operation," said he, " the career of scientific work remains open 

 to me. I can, in spite of the infirmity with which I have been 

 visited, put in order the materials which I have amassed, and 

 even undertake new researches/' 



When this experimental work began again, Plateau showed 

 at once that the clouding of his physical sight had only served to 

 clarify his mental vision. At first he could not give up his inde- 

 pendence, and for some time he wrote between metallic slips ; his 

 assistants soon learned to decipher the writing. Later, however, 

 he gave up this habit, and contented himself with writing to dic- 

 tation. 



His temper was usually calm and equable ; he never uttered a 

 complaint on account of the many deprivations which his blind- 

 ness imposed. He was bright and amusing in his conversation, 

 and yet he was, as all thinkers are, in the main, sober. 



His memory, which was naturally a good one, had become 

 phenomenal by cultivation. It was only necessary to hear an 

 ordinary poem read once or twice for him to be able to repeat it 

 accurately. This gift was one of his greatest compensations for 

 the loss of sight, and of incalculable benefit in his experiments 

 made by the hands of others. His method, given by his son-in- 

 law and biographer, G. van der Mensbrugghe, is as follows : In a 

 day devoted to experiment, speaking of the latter years of the 

 physicist's life, he says : " The old man's face is animated ; he an- 

 nounces with admirable precision all the precautions to be taken 

 that the apparatus should work. According to his often expressed 

 desire, the assistant acquaints him successively with his opera- 

 tions, even to the smallest point. No manoeuvre is left to his 

 personal valuation. The apparatus is at last ready to be set in 

 motion. The master, who imagines and regulates all the disposi- 

 tions, makes still other suggestions ; he assures himself by differ- 

 ent means that all is ready in accordance with his will. At last 

 the assistant is asked to operate the experiment succeeds ! What 

 a satisfaction, what a relief for the noble worker who has con- 

 ceived it ! For greater assurance he causes it to be repeated, with 

 various modifications suggested by the descriptions of the ob- 

 served effects. If all passes as he has foreseen, he at once asks 

 his secretary to write to his dictation all the details of the experi- 

 ment. No point is forgotten, for the provisional wording ought 

 to represent, as exactly as possible, all that had been verified. 

 But if the observation did not meet his expectations, in spite of 

 the precautions he had deemed necessary, the physicist promised 



