i64 



NATURE 



{Dec. 27, 1877 



flower?. When mature, the stigma protrudes consider- 

 ably beyond the indusium. This appears to differ entirely 

 from what takes place in Leschenaidtia. 



" I have recently been much interested with the curious 

 irritability displayed by the stigma of Glossostigma elati- 

 we^/Vz^^, one of the Scrophularinese. The style is dilated 

 towards its apex into a broad spoon-shaped stigma, which, 

 when the flower expands, is closely doubled over the four 

 stamens, entirely concealing them from view. If the front 

 of the bent part of the style is touched it at once springs 

 up, uncovering the stamens, and moves back to the upper 

 lobe of the corolla, to which it becomes closely applied. 

 In this position it remains for a few minutes, and then 

 slowly moves back to the stamens and curves over them 

 as at first. It appears \o me that this irritability of the 

 stigma is simply a contrivarce to insure cross-fertilisation, 

 for an insect crawling into the flower must inevitably 

 touch the stigma, which would then uncover the stamens. 

 On withdrawing, the insect -would be certain to dust itself 

 with pollen, but it would not by this effect the fertilisation 

 of the flower, for the stigma would be then closely applied 

 to the upper lobe of the corolla, entirely out of its way. 

 If the insect were, however, to visit another flower it is 

 evident that it must come into contact with the stigma at 

 its first entrance and would doubtless leave some pollen 

 thereon. The movement of the stigma is remarkably 

 rapid, and its apex must pass through an angle of at least 

 180°. I have been unable to find a record of a similar 

 case, or of so pronounced a degree of irritability in the 

 stigma of any plant. The movement of the lobes of the 

 stigma in Mimulus is much weaker, and is through a 

 much less angle. Yours faithfully, 



" T. F. GHEESEMAN 



" Charles Darwin Esq., F.R.S." 



A TELEPHONIC ALARUM 



THE speaking of the telephone is admittedly so weak 

 that it can only be caught by keeping the instrument 

 in immediate contact with the ear. Hence there is 

 transmitted through the telephone in its present form no 

 sound which would be intense enough to announce to 

 any one who was in a large room and who did not hold 

 the telephone close to his ear, that a message was about 

 to be sent from the transmitting station. The consequence 

 is that a warning apparatus must be attached to the 

 telephone, so that there may be no fear of missing a 

 projected telephonic conversation. 



It is clear that the conducting wire of a telephone can 

 be used to sound a bell as an alarum by means of a 

 current from a galvanic battery, and thereby the defect 

 referred to would be supplied. But the necessary appa- 

 ratus would considerably raise the price of fitting up a 

 telephone apparatus, and besides, one most important 

 property of the telephone, viz., producing the required 

 electric current automatically, would be partly lost. I 

 have, then, invented another warning apparatus, which, I 

 believe, is quite workable. 



Hitherto telephones have been so constructed that only 

 one pole (N in the figure) of the magnet is effective ; I 

 now use also the second pole S, by providing it with a 

 coil of wire, which is simply inserted in the circuit behind 

 the first coil. (The dotted lines in the figure will explain 

 this connection ; the two ends a and |8 are connected with 

 the binding screws fastened to the telephone ; from this 

 the circuit goes to the second telephone.) Before this 

 pole of the magnet may be very easily set up a tuning- 

 fork, A, which, with the telephone, is simply fixed on a 

 resonance case, B ; this arrangement should be made 

 both at the transmitting and receiving stations, and both 

 forks should be in unison. If now the sending station 

 wish to signal that a conversation is to be begun, the 

 fork of that place will be sounded with a fiddle-bow ; the 

 currents thereby induced in the coil are powerful enough 

 to set the fork of the receiving station in such intense 



vibration that the sound may be distinctly heard in a large 

 room ; warned by this signal a person can in the usual 

 way put the telephone to his ear and listen to the words 

 from the transmitting station. And so vice versd. 



I have made an experiment in a large room, when 

 about 100 people were present, and all could hear the 

 sounds of the fork, which in the manner described was 

 set in vibration by a second fork in a distant room. 

 The two forks were Konig Ut^ ; lower forks give less 

 clearly heard tones ; with higher forks I was unable to 

 make any experiment, since I had not two similar ones 

 at my disposal. 



Let me mention two other experiments which I have 

 made. The first is of importance in connection with the 

 question as to how the clang-tints of tones are reproduced 

 through the telephone. In one of the two telephones 

 described substitute for the Ut4 fork a higher one, and 

 sound this by means of a fiddle-bow, and there will be 

 heard with another inserted telephone of the ordinary 

 construction tones of even 12,000 double vibrations per 

 second, a sign that the variations of the magnetic condition 

 of a magnet perceptibly occur, even when the forces pro- 

 ducing these variations change their size 24,000 times in 



a second. This result moreover was not to be expected, 

 since, as is known, magnetic polarisation requires time 

 to accompHsh. Whether these higher tones are com- 

 paratively weaker than the deeper cannot be determined, 

 but probably this is the case. 



In another experiment I used the telephone to test the 

 electric vibrations indicated by Helmholtz and others, 

 which are produced by the opening of the primary cur- 

 rent of an induction apparatus in the induced coil, when 

 the ends of the latter are connected with the armatures 

 of a condenser. For this purpose I inserted the telephone 

 in the circuit between coil and condenser, and observed 

 the effect when the current in the inducing spiral was 

 opened. 



When the ends of the induced spiral were not con- 

 nected with the condenser, I heard a dull report in the 

 telephone ; when, again, these ends were connected with 

 the condenser, this report was accompanied by a shorter, 

 higher sound, whose vibration-number might perhaps be 

 determined by a musical ear ; a proof of the existence of 

 the vibrations mentioned in the last case. The observa- 

 tions were made with a telephone, the iron membrane o£ 

 which was very thin and had a yery deep tone. 



' ' W. C. RONTGEN 



