Mr. Presiding Justice Baumedelivered the opinion of the court.
4. Landlord and tenant. § 84*—inadmissibility of parol evidence to aid construction. Where a bill to restrain the interference with a certain water supply reserved to the complainant in a lease predicates a right to relief upon an alleged oral agreement entered into between the lessor and lessee contemporaneous with the written contract under seal, it is inadmissible to vary the terms of the written conti-act, as the leasehold contract cannot rest partly in writing and partly in parol. 5. Landlord and tenant, § 84*—when the doctrine of practical construction may be invoiced. In an action to restrain a lessee from interference with lessor’s water supply alleged to be reserved in a lease, the doctrine of practical construction may only be properly resorted to when the terms of the contract are uncertain and ambiguous.