366 . SCIENTIFIC CONGRESS OF CAELSRUHE. 



none could be more competent, especially as the object is not so much 

 a course of methodical instruction as the exposition of unconnected 

 facts, supported by experiments aptly chosen and dexterously executed. 

 It is in this line that M. Boettger particularly excels, for an extraor- 

 dinary and peculiar facility seems to qualify him for the contrivance 

 and execution of the most difficult experiments, without the necessity 

 of a previous theory or system of ideas. Thus, in 1847, he prepared 

 gun-cotton before the secret of its preparation was known, and without 

 any other guide than the name of fulminating cotton, or other starting 

 point than the xyloi'dine or nitrous fecula discovered by Braconnot. 

 We may add that he made no secret of his discovery, but hastened to 

 give it to the public. In like manner, having heard, some years after- 

 wards, as all the rest of the world did, of the decisive experiment by 

 which M. Faraday had discovered the action of an electro-magnet on 

 polarized light, M. Boettger repeated the experiment with success, 

 and published the manner of operating before the process which had 

 been followed by the illustrious savant of England was known. 



As M. Boettger is an assiduous frequenter of scientific reunions, he 

 has often afforded them entertainment by attractive experiments, and 

 by a dexterity of hand which might have won success even on a differ- 

 ent stage. A simple exhibition of his, during the present session, 

 seems not unworthy of notice. Having taken a goose quill, he pressed 

 it down so as to bend it together in several'places. The quill was not 

 broken, but there were evidently folds ; nor was it capable of being 

 held upright and rigid as before. But a few manipulations by the 

 operator quickly restored it, so that no trace of the folds recently so 

 conspicuous, remained. The explanation is, that the quill had been 

 first immersed for some moments in hot water and then plunged into 

 cold; and the theory on which the result depends is, that the sudden 

 contraction sustained by the corneous substance, previously distended 

 by the warm water, enables the quill to recover its original rigidity. 

 This process might doubtless be of service in restoring plumes used 

 for personal decoration. 



At the same session Mr. Boettger showed that a slender jet of water 

 may serve as an electroscope. If a glass rod, which has been previously 

 rubbed with a piece of cloth, be presented to such a jet, the thread of 

 water is seen to change its form. If the rod approaches it from above, 

 the small drops unite and fall in large drops ; if, on the other hand, 

 the rod is presented near the base, the height of the jet is diminished. 



This experiment seemed to be given by M. Boettger in good faith 

 as of his own invention, and was apparently received as such by all 

 present, including some names of the highest distinction in science. 

 Neither M. Muller, who has published a work on the progress of elec- 

 tricity, nor M. Buff, who regularly compiles a record of the progress 

 made in physics during each year, nor M. PoggendorfF, whose cele- 

 brated annals are especially open to physical researches, reminded the 

 speaker that this experiment had been previously published by a Ger- 

 man physicist. It was evidently because they themselves did not 

 remember it. 



We see frequent examples of this, arising, no doubt, from the multi- 

 tude of new observations which every day gives birth to. If we dwell 



