SCIENTIFIC READINGS. 123 



260. At what rate does sound travel in water ? 



261. In what do sound and light resemble each other ? 



262. Which is the best conductor of sound, brick or 

 stone ? 



263. What is an Echo ? 



264. Why can a person in the whispering-gallery of 

 St. Paul's, hear another distinctly, if he speak in a 

 whisper on the opposite side ? 



265. Why are the repetitions of an echo more nume- 

 rous in the night-time than in the day ? 



266. Describe the Speaking Trumpet. 

 267- Describe the Invisible Girl. 



268. Required the distance of a thunder- cloud, if a 

 space of thirty seconds intervene between the lightning 

 and the thunder. 



269. Heard the report of a gun from a ship at sea, 

 when just twelve seconds before, the flash was seen ; re- 

 quired the distance of the ship. 



270. What space of time will intervene between the 

 flash and report of apiece ofordnancefifteenmiles distant? 



2/1. If I hear the echo of my voice from a building just 

 eight seconds after I speak, at what distance will the 

 building be from me ? 



METEOROLOGY. 



272. What is Meteorology? 



273. How high does the atmosphere extend ? 



271. What is the average quantity of aqueous vapour 

 contained in the atmosphere r 



275. How much lighter than water is the atmosphere ? 



276. Through what means is it that water is sus- 

 pended in the atmosphere? 



277. What quantity of water is supposed to be taken 

 up annually by the atmosphere ? 



278. What quantity is carried off by evaporation from 

 the Thames in a summer's day, and what quantity from 

 the Mediterranean in the same time ? 



279. What is the cause of Rain ? 



280. What was Sir Richard Phillips's plan for fertili- 

 zing barren lands ? 



G 2 



