THEKMOMETRIC SCALES.] 



APPLIED MECHANICS. 



907 



To reduce temperature by Fahrenheit to temperatur 

 by Centigrade. 



Rule. Subtract 32, multiply by 5, and divide by 9. 



Example 1. To reduce 180 Fahrenheit to Centigrade 



180 

 Subtract . . 32 



148 X 5 

 9 



82 -222 Centigrade. 



Example 2. To reduce 15 Fahrenheit to Centigrade. 



15 

 Subtract . . 32 



17 X 5 

 9 



9" -44, &o., 



or 9 -44, (fee., below zero. 



To reduce temperature by Centigrade to temperature 

 by Fahrenheit. 



Itule. Multiply by 9, divide by 5, and add 32. 



Example 3 To reduce 82 -2 Centigr. to Fah. 

 Multiply by . . 9 



Divide bj 

 Add 



6)740 nearly 



148 

 . 32 



180 Fah. 



Example 4. To reduce 9 3< 4 Cenligr. to Fah. 



9 



Divide by 

 Add 



6) 85 nearly 



-17 

 32 



15 Fah. 



Note. When the temperature has the mark (minus) 

 prefixed, it means below zero, and is to be subtracted 

 in cases where it would be added if it had not the 

 mark . 



Example 5. To reduce -100 Centigr. to Fah. 

 9 



5) -900 



- 148 Fah. , or 148 below zero. 



To reduce temperature by Fahrenheit to temperature 

 by Reaumur. 



liule. Subtract 32, multiply by 4, and divide by 9. 



Example 6. To reduce 62 Fah. to Reau. 

 Subtract ... 32 



Multiply by 

 Divide by . 



30 

 4 



9)120 



13 3 Reau. 



Example 7. To reduce 15 Fah. to Reau. 

 32 



-17 

 4 



9) -68 



7 '5 Reau , or 7 5 below zero. 



To reduce temperature by Reaumur to temperature by 

 Fahrenheit. 



Rule. Multiply by 9, divide by 4, and add 32. 



Example 8. To reduce 13 3 Reau. to Fah. 

 9 



4)120 



30 

 32 



62 Fah. 



Example 9. To reduce - 7 0i 5 Reau. to Fah. 

 9 



4) -68 



-17 

 32 



15 Fah. 



To reduce Centigrade to Reaumur. 

 Rule. Subtract th. 



Example 10. To reduce 85 Centigrade to Reaumur. 

 One-fifth . . . . 17 



C8 Reau 



To reduce Reaumur to Centigrade. 

 Rule. Add Jth. 



Example 11 To reduce 68 Reaumur to Centigrade. 

 One-fourth ... 17 



85 Centigr. 



DIVISION OP THE CIRCLE. 

 CO Seconds = 1 Minute 60* =- 1' 

 60 Minutes = 1 Degree CO' = 1 

 90 Degrees = 1 Quadrant or right 



7T 



angle, often marked -5 



SCO Degrees or 4 Quadrants = 1 Circumference, 

 often marked 2 ir. 

 THE FRENCH DIVISION 13 

 100 Seconds = 1 Minute. 

 100 Minutes = 1 Degree. 

 100 Degrees = 1 Quadrant. 



4 Quadrants= 1 Circumference. 



The quadrant, right angle, or quarter of the circum- 

 ference, is the same for the French and English systems, 

 and 100 French are therefore equiva'ent to 90 English. 

 To reduce French degrees to English. 

 Rule. Subtract ^th. 



Example 1. To express 73 French in English measure. 

 Subtract one-tenth . 7 '3 



Multiply by 



65-7 

 60 



65 42' English. 



To find minutes . 42 



Example 2. To express 2C 7' 35" French in English 

 measure. 



The French number would be written 26 -0735 



Subtract one-teiith 2 -60735 



23 -46615 

 60 



27 -909 



60 

 Am. 23" 27' 58" -14 English. 



68-14 



To reduce English degrees to French. 

 Rule. Add Jth. 

 Example 3. To express 65" 42' English in French 



42 

 measure. 42'=^ orO'7; therefore the English, ex- 



ressed decimally, is 65'7 

 Add one-ninth . 7 '3 



73 French. 



