2. Every person who purports to have skill in la business, and undertakes for hire to perform it, is bound to do it with ordinary skill, and is res-ponsible civilly in damages for the want of it; 11 M. & W. 483; and sometimes he is responsible criminally. Vide Mala Praxis; 2 Russ. on Cr. 288,

3. The degree of skill and diligence required, rises in proportion to the value of the article, and the delicacy of the operation: more skill is required, for example, to repair a very delicate mathematical instrument, than upon a common instrument. Jones~ Bailm. 91; 2 Kent, Com. 458, 463; 1 Bell~s Com. 459; 2 Ld. Raym. 909, 918; Domat, liv. 1, t. 4, §8, n. 1; Poth. Louage, n. 425; Pardess. n. 528; Ayl. Pand. B. 4, t. 7, p. 466; Ersk. Inst. B. 3, t. 3, §16; 1 Rolle, Ab. 10; Story~s Bailm. §431, et seq.; 2 Greenl. Ev. §144.