Q about ACL: Chapter 13: Exercise 3b

For this exercise in Graham's "ANSI Common Lisp", when I add declarations to the ray-tracer program, it actually runs slower. Can anyone explain to me why that is?

My code with declarations is available here: http://www.automatous-monk.com/lisp/aclp/chap13-exer03.html

I'm not sure, but I believe I was using SLIME when I did this exercise (it was a while ago).