KNOWLEDGE 



July 16 at lOJ o'clock. 

 July 20 at 10 o'clock. 

 July 24 at 9| o'clock. 



NIGHT SKY FOR JULY (Secoxd Map of Pair), 

 Showing the heavens as they appear at the following hours : — 



I July 27 at 9i o'clock. I August S at SJ o'clock. 



July 31 at 9i o'clock. August 12 at 8i o'clock. 



I August 4 at 9 o'clock. | 



IS insopnr 





,.f i 



<iW 



intC substance, G. Wlieatstone used a Leyden 

 I't being to ascertain tlie speed at which 

 avolled. But any other form of condenser 



sidcr 



capable (with the aid of suitable apparatus) of being 

 distinguished. 



Let tis call to our aid the (what I may style classical) 

 experiment of Sir Charles Wheatstone. The accompany- 

 ing diagrams illustrate the experiment. P and N (Fig. 1) 

 are two pieces of metal separated by a glass plate or 



5 of a'quar 



;r of a 



lull 



not touching it, 

 connected, by means of a MimlirUuL 

 ball E. This, in its turn, is i.luccu 

 ig, F. There are thus three p; 



the ■" ' - - - 



event, therefore, of the chained plates P N being 



