SCIENTIFIC AND TECHNICAL LABOURS TO 1850. 115 



sur la telegraphic electriqtie" and the corresponding 

 paper in PoggendoriFs Annalen, as the most important 

 particulars have been interwoven in the general nar- 

 rative, and have thus already received detailed con- 

 sideration. 



When in the year 1842 I applied for my first 

 Prussian patent no process of galvanic gilding or silver- 

 ing was known in Germany. 



I had experimented with all the gold and silver 

 salts known to me, and besides the hyposulphites had 

 also found the cyanides suitable. The patent however 

 was only granted me for the former, as in the mean- 

 time Elkington's English patent for the employment 

 of the cyanide salts had become known. Notwith- 

 standing the beautiful gold and silver precipitates ob- 

 tainable from hyposulphite salts, the cyanide salts have 

 in the long run kept the field, their solutions being 

 more constant. 



The problem proposed to my brother William to 

 construct a regulator, which should so exactly regulate 

 a steam-engine connected with a water-wheel, that the 

 water-wheel should always perform its full work, but 

 the steam-engine yield the required excess of working 

 power, led me to the idea of the so-called differential 

 regulation. It consisted in employing a freely- oscil- 

 lating circular pendulum for the production of a per- 

 fectly uniform rotation, thereby causing the turning of 

 a screw, whilst the engine to be regulated turned a 



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