494 Additional Notes, 



Thermo77ieter. p. 103. 



In Fahrenheit's Thermometer the fy^eezing point is 

 fixed at S2 deg. and the boiling point at 212 deg. In Reau- 

 mur's, or rather De Luc's, the freezing point is 0, and the 

 boiling point 80 deg. In De L'Isle's, the usual order of 

 graduation is inverted, the freezing point being 1 50 deg. and 

 the boiling point 0. And, finally, in the thermometer of 

 Celsius, the point of freezing is marked 0. and that of boil- 

 ing 100 deg. To reduce the degrees of Reaumur to those 

 of Fahrenheit, the following formula may be employed : 



+32=F. To reduce the degrees of Celsius to those 



C X 9 



of Fahrenheit, the following is sufficient: — — — 4-32=F. 

 To reduce the degrees of De L'Isle, under the boiling point, 

 to those of Fahrenheit, say 212— -g-=F. To reduce 

 those above the boiling point to Fahrenheit, say, 212 + 



?^==F 



5 ' 

 Though Newton first pointed out the method of making 

 tolerably good thermometers, the practical part of the art of 

 forming and graduating them was greatly simplified by Mr. 

 Fahrenheit, of Amsterdam, and by Dr. Martine, of 

 St. Andrews, whose Essay on the Construction and Gradua^ 

 tion of Thermometers is one of the best works on the sub- 

 ject extant. Professor Van Swinden, also, of Franeker, 

 and M. De Luc, of Geneva, have written very ably and 

 instructively on the subject of thermometers. 



Eudiometers, p. 105. 



The numerous Eudiometers proposed by different Che- 

 mists may be reduced to Jive. 



1. The first is that invented by Dr. PivIestley, in which 

 jiitrous gas is mixed, over water, with the air, the purity of 

 which it is wished to ascertain. The diminution of the 

 volume of this mixture is proportioned to the quantity of 

 oxygen contained in the air, which is rapidly absorbed by 

 the nitrous gas, and the nitric acid thus formed is also rapidly 

 absorbed by the water. This eudiorneter has received various 



