While the intention of the parties must appear from the language which they used together with the surrounding facts and circumstances, it is sufficient if such intent can be ascertained with reasonable certainty.1 It may be sufficiently clear without being a "work of art."2 The ordinary rules of construction may be invoked to ascertain the intention of the parties and to save the contract from being rendered invalid for uncertainty.3 A contract of sale is not uncertain, because the number to be delivered is fixed only approximately,4 or because the sale is by number and the payment is to be by weight.5 A promise to attempt to raise a certain amount of subscriptions is not so uncertain, by reason of its failure to describe such attempt, that it is not a consideration for a subscription.6 A contract to give a mortgage on certain property is sufficiently definite, although the terms of the mortgage are not given, since the usual form of mortgage will be assumed to have been intended.7