424 



♦ KNOWLEDGE 



[Nov. 21, 1884. 



NIGHT SKY FOR NOVEMBER AND DECEMBER. 



First Map of Pair. 



NoTember 7 at 10 o'clock. 

 November 10 at 9| o'clock. 

 November 14 at 9^ o'clock. 



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



November 18 at 9i o'clock. 



November 22 at 9 o'clock. 



November 26 at SJ o'clock. 



November 30 at SJ o'clock, 

 December 4 at 8i o'clock. 

 December 7 at 8 o'clock. 



& Co. give great prominence in their system. Briefly it is 

 known as the " Syphon Theory," which consists in the 

 followin" : where a compartment has to be ventilated 

 entirely from above {e.g., on ship-board), the fresh air will 

 descend the shorter shaft and the foul air will ascend the 

 longer, but, from experiments which have from time to 

 time been conducted, we should say this is modified by a 

 variety of causes, and is true in extreme cases only. How- 

 ever, the importance of extracting the foul air from the 

 highest available point in the room or building cannot be 

 too much insisted on. In conclusion, we would earnestly 

 ommend to the careful consideration of our readers the 



subject of ventilation, whether of houses or ships, aot 

 for<Tetting, however, those necessary evils, house-drains ; 

 and it is to be hoped that the few remarks which we have 

 here offered may enable them to understand the modv^ 

 operandi of the " Natural VentUation " schemes at present 

 before us. 



T 



FIRST STAB LESSONS. 



By Richard A. Proctor. 



IHE map of the stellar heavens, as P^f^Jf'j^*'^^ J^**^^ 

 needs scarcely any explanation. '"' " " " «!0"«> 



It will be observed 



