460 Proceedings of Learned Societies, 



the further side is in shadow of intense blackness ; and from the 

 same cause the sky, as seen from the moon, would appear perfectly 

 dark, the stars being always visible. 



The day in the moon is a fortnight in duration, and during 

 this period the temperature on the illuminated side would pro- 

 bably rise to 220° Fahrenheit, or hotter than boiling water. The 

 night would be of equal length, and during this time the heat, 

 from the absence of aqueous vapour and atmosphere, would be 

 radiated freely into space, and the temperature would fall to that of 

 space, viz., to 300° below zero Fahr. The absence of air and water 

 in the moon would render impossible the existence of animal and 

 vegetable life corresponding to that which prevails on our globe. 



The use of the moon, as a satellite of the earth, is usually 

 regarded as being that of a luminary, but from its variable action 

 this use must be regarded as secondary. Its value as inducing 

 the tides and currents of the ocean is of greater importance, both as 

 conducing to the sanitary condition of the sea, and as aiding transit 

 in rivers, by the ebb and flow of the tide. At the conclusion of the 

 lecture, Mr. Nasruyth illustrated the formation of the radiating 

 cracks on the moon's surface, by congealing water in a thin 

 glass globe hermetically sealed — when it cracked in lines radiating 

 from a single point — the cracks in the moon being attributed to the 

 contraction of its external hardened crust during the period of its 

 rapid congelation. 



June 10. 



New Magnetic Experiments. — Professor Tyndall concluded the 

 series of Friday evening discourses, at the Royal Institution, by a 

 Lecture " On a New Magnetic Experiment." After demonstrating 

 the familiar properties of magnetized bodies, he entered into a con- 

 sideration of the changes of arrangement which the molecules of a 

 piece of soft iron must undergo when it is converted into a tempo- 

 rary induced magnet, by the passage of a current of electricity 

 through the coils of copper wire surrounding it. These molecular 

 changes are proved by the fact that, when a bar of soft iron is mag- 

 net ized and demagnetized, in succession, by rapidly breaking and 

 remaking the current in the surrounding coil of wire, it is thrown 

 into a state of vibration which produces a sound in the air. Tins 

 alteration of the molecular arrangement was supposed by Ampere to 

 be attended with a shortening of the bar of soft iron. Mr. -Joule, 

 however, lias proved that tin; bar is actually long! honed when it is 

 converted into an induced magnet. The experiment demonstrating 



this fact was shown in public for the first time. 



A bar of Boft iron, two feet in Length, was firmly Beoured in an 

 erect, position. On its upper extremity was a vertical rod of brass,, the 



lower end of which rested OH the top of the iron bar; the upper, 

 tipped with a steel point, pressed against a small plate of agate, 

 near the. fulcrum of a horizontal lever. A h f la; distant end of the 

 lever was :i very fine wire, which war, kept coiled a,round an axis by 

 the tension of a fine hair spring. This axis turned a small mirror. 

 The action of this exceedingly delicate instrument is easily ex- 



