85 



CHAPTER V. 



ON GLASS. 



FAHRENHEIT AND REAUMUR. GLASS FIRE SCREEN. ICE WINDOWS. 



GLASS OF POMPEII. VENETIAN GLASS. GLASS WINDOWS IN 



ENGLAND. DISCOVERY OF GLASS. SAND. BARONS* CAVE AT 

 REIGATE. BARILLA. KELP. FUCI, USES OF. FUCUS NATANS. 



WRACK. FUCUS TENAX. LAMINARIJE. FUCUS CRISPUS. DULSE. 



LAVER. GELIDIUM. CHINESE SWALLOW. SOY. RED SNOW. 



HENRIETTA. 



I DID not like to interrupt you, aunt, in the garden; but 

 when you were telling us about the steppes of Asia, you 

 talked of the heat being at 30 of Reaumur.* .How high is 

 that in our thermometer 1 ? 



MRS. F. 



Ours, and indeed most of the thermometers used in Eng- 

 land, are graduated by Fahrenheit's scale, whereas on the 

 Continent, Reaumur's is more frequently employed. The 

 difference is this, that in Fahrenheit's scale, the freezing 

 point is placed at 32 degrees, whereas in Reaumur's it is at 

 zero. The degrees also of Fahrenheit's are less than Reau- 

 mur's in the proportion of 9 to 4: that is, nine degrees of Fah- 

 renheit are only equivalent to four of Reaumur. 



HENRIETTA. 



How then do you convert one into the other? 



MRS. F. 

 To bring Fahrenheit into Reaumur, you multiply by four 



* See page 62. 



