148 Notes and Memoranda. 



On the Eigidity op the Eabth. — Professor Wm. Thompson shows that 

 nnless the earth were composed of very rigid materials, it woiudyield under the tide- 

 generating forces exerted by the sun and moon, to such an extent as would sensibly 

 diminish the actual phenomena of tides and of precession and mutation. The upper 

 crust of the earth is possibly, on the whole, as rigid as glass, more probably less 

 than more ; but as a whole the earth must be far more rigid than glass, and pro- 

 bably more so than steel. Hence the interior must on the whole be more rigid, 

 probably many times more rigid, than the upper crust. This calculation con- 

 firms the views of Mr. Hopkins, and is quite inconsistent with the hypothesis that 

 the earth is a mass of melted matter enclosed in a thin solid shell. Mr. Hopkins 

 has shown that this crust cannot be less than 800 miles thick. Professor Thomp- 

 son considers that no thickness less than 2000 or 2500 miles would enable it to 

 resist the tide-generating force of the sun and moon so as to leave the phenomena 

 as they are actually found. — Proc. Royal Soc. No. 50. 



Distkibution of Nerves. — la a paper communicated to the Eoyal Society 

 Mr. Lionel Beale states : " The nerves distributed to the voluntary muscles of 

 the frog do not terminate in free ends, but there is reason for believing that 

 complete nervous circuits exist. In all cases, the fibres resulting from the divi- 

 sion of the ordinary nerve fibres are so fine that many cannot be seen with a less 

 magnifying power than 1000 diameters, and there is evidence of the existence of 

 fibres which could only be demonstrated by employing a much higher magnifying 

 power. It is by these very fine fibres alone, and their nuclei, that the tissues are 

 influenced. The ordinary nerve fibres are only the cords which connect this 

 extensive peripheral system." The author finds the same arrangement in the 

 nerves of man and the higher mammals, and also in the invertebrata. He 

 employs a highly refractive fluid, such as syrup or glycerine, in these investiga- 

 tions. — Proc. Royal Soc. No. 50. 



Mechanism oe the Human Voice. — By means of the laryngoscope, Mr. 

 John Bishop has succeeded in watching the movements of the larynx during the 

 utterance of vocal sounds. When the lower tones are made, the vocal cords vibrate 

 through their whole length. As the pitch rises, the vibrating length diminishes, 

 and the cords are pressed more closely together. In falsetto notes, it is only the 

 extreme end of the cord that vibrates. Moreover, the vocal chords form a kind 

 of valve, which is situated in a tube, and acts like a reed. Thus the organs of the 

 voice perform the double office of reed and string. — Proc. Royal Soc. No. 50. 



Me. Lassell and the Moon. — At Malta, where Mr. Lassell has erected his 

 magnificent 4-feet reflector, he observes the details of the moon with a sharpness 

 and distinctness which he had never seen before. He states that, if a carpet 

 the size of Lincoln's Inn Fields were laid upon its surface, he could tell whether 

 it was roxmd or square. He adds, in a letter to the President of the Eoyal 

 Society, " I see nothing more than a repetition of the same volcanic texture — the 

 same cold, crude, silent, and desolate character which smaller telescopes usually 

 exhibit." 



The Formation of Haxos. — Sir John Herschel has devised an elegant 

 mode of illustrating the action of minute refracting spheres. He mounts the 

 spores of the common puff-ball in a film of oil between two pieces of glass. When 

 these are held close to the eye, and a candle viewed through them, beautiful 

 concentric halos appear. 



Optical Experiment. — Mr. Slack calls attention to concentric circles of 

 light, exquisitely marked by fine black intersecting lines, which may be seen by 

 taking a stout glass tube, about one-eighth of an inch in diameter and six or 

 eight inches long, holding it horizontally opposite the flame of a candle, and 

 looking at the light throiigh it. A piece of paper rolled round the tube shuts 

 out all unnecessary illumination, and makes the phenomena more clear. 



