SENSITIVE FLAMES, ETC. 185 



extremely exalted temperature, a few of the elements 

 yield simple vibrations corresponding to the vibrations of 

 a pendulum or tuning-fork. For example, the metal 

 platinum and the metal sodium approach these simpler or 

 pendular vibrations, having spectra of extreme simplicity. 

 Other elements yield a complex vibration corresponding 

 to a compound tone, giving rise, therefore, to intricate wave 

 forms. We may instance, as examples of this quality, 

 iron and chromium, and as there is a definite relationship 

 between the upper partial tones of a compound tone and 

 its fundamental tone, so the question has been asked, " Is 

 there any definite relationship existing between the various 

 constituent vibrations of a glowing molecule of iron and a 

 glowing molecule of chromium? " This question has been 

 answered, in fact, with some success by Mr. Johnstone 

 Stoney. Time will not allow me to enter more fully into 

 this matter, but it seems to open up a pathway for future 

 discoveries. 



.Let us now, for a moment, regard the transference of 

 this vibratory energy to our senses, or our instruments. 

 It is evident that some medium is necessary. The coarser 

 molar vibrations of sound are readily and rapidly trans- 

 mitted by solid, liquid, and gaseous bodies. For example, 

 if I take this long rod and hold it against a wooden 

 surface, we get here transmission of the vibration of a 

 tuning-fork through the rod to the wood in the distance. 

 So, in like manner, water is found to transmit the vibra- 

 tions of sound, and air is found to do the same, as in the 

 case of the sounds which I am now uttering. The rate of 

 the transference of this molar vibration to the medium 

 around has been examined with great care by physicists 

 both theoretically and experimentally. It will be needless 

 for me to refer to the investigations now, but this piece of 

 apparatus which is exhibited in the Loan Collection is ex- 

 tremely interesting, as being the very instrument whereby 

 the velocity of sound in water was determined by those 

 eminent physicists Colladon and Sturm (Fig. 1). They 

 plunged this large spoon-shaped metal tube into the water, 

 and at some distance off a boat was moored, and under the 

 water near the boat a bell was struck. The moment that 

 the bell was struck, a brilliant light was made to appear 

 in the boat. The observers in a distant boat noticed the 



