A challenge interposed on account of an ascertained or suspected bias or partiality, and which may be either a principal challenge or a challenge to the favor. Harris- burg Bank v. Forster, 8 Watts (Pa.) 300; State v. Sawtelle. 00 N. H. 488. 32 Atl. S31: Jewell v. Jewell. 84 Me. 304, 24 Atl. 858. 18 L. R. A. 473