70 THE LAW AFFECTING ENGINEERS 



Where parties have used language which admits of two con- 

 structions, the one contrary to the apparent general intent, 

 and the other consistent with it, the law assumes the latter to 

 be the true construction (Walker v. Giles, 1848, 6 C. B. 662, 

 702). The legal meaning of a number of words and phrases 

 which are commonly used in contracts will be found in 34, 

 post. 



11. Whether parol evidence admissible in relation to a written 

 contract. Inasmuch as engineering contracts are generally 

 reduced into writing, it may be necessary to consider whether, 

 in case of a dispute, that writing can be varied or explained 

 by parol evidence. Generally speaking, where there is no 

 ambiguity in the terms of a written contract, the agreement 

 or document itself is the only criterion of the intention of 

 the parties. Hence parol evidence contradictory to the writing 

 itself must be excluded, even though such evidence might 

 show that the real intention of the parties was at variance 

 with the particular expressions used in the written instrument 

 (Hitchin v. Groom, 1848, 5 C. B. 515). But the proviso that 

 this rule only applies where there is no ambiguity makes a 

 world of difference ; and it may be laid down as a general 

 principle that parol evidence will be admitted : 



(i.) To show that words in the contract were used in a 

 particular sense ; 



(ii.) To explain a latent ambiguity ; 



(iii.) To prove a custom or usage of trade to which the 

 agreement was subject (see 13, 14, 15, post) ; 



(iv.) To show that one or other of the parties was acting as 

 agent for some third person ; 



(v.) To identify the subject-matter of the contract if it be 

 uncertain ; 



(vi.) To show that the alleged agreement is not the whole 

 agreement between the parties ; 



(vii.) To defeat an agreement on the ground of illegality, 

 duress, or fraud. 



The law was thus stated in Myers v. Sari, 1860, 30 L. J. 

 Q. B. 9 : " Where terms in the particular contract have, 

 besides their ordinary and proper sense, also a scientific or 

 peculiar meaning, the parties who have drawn up the contract 

 with reference to that particular department of trade or 

 business must fairly be taken to have intended that the words 



