2 Metaphors for efficacies

Secret service has been long a term of great use to the ministers of this nation; a term of art to which such uncommon efficacy has been hitherto annexed, that the people have been influenced by it to pay taxes, without expecting to be informed how they were applied, having been content with being told, when they inquired after their properties, that they were exhausted and dissipated in secret service.

Moreover, from the employer's standpoint, the efficacy of female labor will be largely a matter for experiment, and "equal pay" will give him no inducement to experiment at all.

2 Metaphors for  efficacies