30 Gee, Daltorfs Lectures and Lecture Lllustrations. 



but in No. 32 (io/ / X32 // ) the values for ether are also 

 shown. Dalton's law may be given in the form : — 



log p = A + BO 



where p is the pressure, A and B constants, and the 

 absolute temperature. Modern experiments have shown 

 that 



more nearly expresses the law for water. 



Sheets 34 and 35. 



These are smaller diagrams ( 19" x 24") and have no 

 lettering. They were used by Dalton in his earlier 

 lectures, when dealing with the steam engine. No. 35 

 explains the method of Savary (1698) for raising water 

 by suction into a vacuum produced by the condensation. 

 In the diagram a safety valve is shown which was not 

 applied by Savary, but invented in 17 17. 



No. 36 is Newcomen's engine (1705-7). The diagram 

 shows the method of injection into the cylinder, but no 

 safety valve or method of feeding the boiler is represented. 



Sheet 36. 



(2o"xi5".) Leslie's experiment on the reflection of 

 heat. In the focus of one concave mirror is placed a 

 bottle of hot water ; in the focus of a second concave 

 mirror is an air thermometer. 



Optics. 

 Sheet 37. 



(13" x 19".) Shows (1) a parallel beam and a diverg- 

 ing beam of light, (2) the reflection of a parallel beam 

 from a plane mirror, (3) the refraction of a parallel beam 

 in passing through a prism, and (4) the diffraction of a 

 parallel beam when passing through a small opening. 



