Effi*ca"cious*ly

from The Collaborative International Dictionary of English v.0.48

Efficacious \Ef`fi*ca"cious\, a. [L. eficax, -acis, fr.
   efficere. See {Effect}, n.]
   Possessing the quality of being effective; productive of, or
   powerful to produce, the effect intended; as, an efficacious
   law.

   Syn: See {Effectual}. -- {Ef`fi*ca"cious*ly}, adv.
        [1913 Webster]