E C C 



2. For walls with an interior slope, or a slope towards the bank, let 

 the base of the slope be - of the height, then 



where m .0424 for vegetable or clayey earth, mixed with large gravel ; 

 m = .0464 if the earth be mixed with small gravel j m = .1528 for sand ; 

 and m = .166 for semifluid earths. 



Ex. Let the height of a wall be 20 feet, and _L of the height for the 



20 



base of the slope, suppose also the specific gravity of the wall and bank 

 to be 2600 and 1400, and the earth semifluid j then 



=i 5 feet, while the thickness of the wall at the bottom 

 will be 6 feet. 



RASTER, to find it on any year. '(Delambre.) 



1. Divide the year proposed by 19 Call remainder a. 



2. Divide the same number by 4 Call remainder b. 



3. Divide it also by 7 Call remainder c. 



4. Divide (19 a -f- M) by 30 Call remainder d. 



5. Divide (2& + 4c + 6d-fN)by7 Call remainder e. 



6. Then Easter day will fall either on (22 -f- d -f- e) of March j or on 



(d _|_ _ 9) of April. 



Values of M and N in the above calculation. 



M. N. 



From 1700 to 1799 23 3 



1800 to 1899 23 4 



^900 to 1999 24 5 



Exceptions to this rule : 



1. If the computation give April 26, substitute the 19th. 



2. If it give April 25, substitute the 18th. 



ECCENTRICITY of a Planet's orbit (Woodhouse, Playfair.) 



Let e be the eccentricity of the orbit, g the greatest equation of the 



centre, found by observation, and put 5?0 ^9573 = A * then 



