120, 121.] PERFORATED SOLID. 139 



so that 



We saw above that 



so that we may also write 



Again, by Statics, 



x a = P K i \\( n y - mz) da l + &c., 

 whence finally, 



with similar expressions for the remaining components of the 

 impulse. We have here written for shortness 



\ = p 



&c. &c. 



