Reid, J. - (1.)THE appellant is the owner of the Jharia estate. In 1898 his predecessor granted a mining lease of a part of that estate to the predecessor of respondent No.1. THE terms of that lease are set out in a kabuliyat of October 22, 1898, which begins: "this kabuliyat regarding Mourushi Mukarrari, i. e. permanent settlement on commission of coal land is executed to the following effect. " THE provision, the meaning of which is in dispute in the present litigation, is as follows : 1. That for the quantity of coal which I shall raise from the leasehold entire 1103 bighas 18 kathas of coal land of Ekra I shall pay commission, i. e. , royalty on steam coal, rubble coal, hard coke and soft coke at the rate of 3 annas per ton and for rubble and dust for burning bricks at 1 anna 6 pies per ton. Be it stated that I shall pay royalty at the present fixed rate for the coals, which will be despatched by the East Indian Railway line, But in future if the Bengal Nagpur. Railway line is constructed and the freight of coal becomes less by 2 annas at least or more than what is fixed at present per ton, I shall pay royalty for those coals, which shall be despatched in the aforesaid manner at the said reduced freight, at 5 annas per ton on steam, steam rubble, soft coke and hard coke and 2 annas 6 pies per ton on rubble and dust for burning bricks. But if the said railway freight becomes less than 2 annas per ton, the amount which will be reduced will be enhanced on the rate of royalty at present fixed on steam, steam rubble, soft coke and hard coke and enhanced by half thereof on rubble and dust for burning coal.
(2.)THERE follows a number of other provisions for an annual minimum royalty, for interest, for hypothecation of the tenant's property at the colliery and for other matters which need not be further referred to at this point.
In 1898 when the lease was granted the only railway available for transport of coal from this district was the East Indian Railway, but it was contemplated that the Bengal Nagpur Railway might be extended so as also to serve this district. The Bengal Nagpur Railway was so extended and the extension was opened for traffic in 1908. At the time when the lease was granted the freight for coal from the colliery to Calcutta was Rs. 8 annas 11, but in 1902 this freight was reduced to Rs. 8 annas 2, and after some fluctuation both the East Indian Railway and the Bengal Nagpur Railway maintained the freight at Rs. 3 annas 2 from 1904 for many years.

The interpretation of the clause quoted above gave rise to litigation in 1910 between the then lessor and lessee. This litigation ended in an appeal to His Majesty in Council and the judgment of their Lordships was delivered on March 8, 1917, by Lord Parmoor. The question at issue was whether the lessor was entitled to the enhanced rate of royalty provided in that clause, and after quoting the clause the judgment proceeded : The royalty clause fixes a royalty of 8 annas per ton of steam coal, steam rubble, hard and soft coke, and of 1 anna 6 pies per ton of brick burning rubble and dust, raised and despatched or sold by the lessee. These latter words are important in construing the clause. A contrast is drawn between coal or rubble despatched and coal or rubble sold at the pit's mouth, and the claim for an enhanced royalty on coal is made in respect of coal despatched by rail. It does not appear, and it is not material, whether at the date of the lease any coal was despatched in any other way than by rail. The only railway which served the coal field at the date of the lease was that of the East Indian Company. The clause provides that royalties at the present fixed rate should be paid on all coal despatched by the East Indian Company, subject, however, to a future contingency : But if, in future, the Bengal Nagpur Railway being constructed, the freight on coal is reduced by 2 annas or more per ton then on all coals despatched in the aforesaid manner (ukta rupey) at reduced (Kom) rates royalty would be paid at 3 annas per ton of steam coal, steam rubble, hard and soft coke, and 2 annas 6 pies per ton of brick burning rubble and dust. The Bengal Nagpur Railway has been constructed, and it has been correctly held in both courts that, as a consequence of this construction, a readjustment was made in the freight on coal. It was further assumed throughout the hearing, both before the Subordinate Judge and in the High Court, that, in the readjustment, the freight on coal had been reduced by more than 2 annas per ton as compared with the freight in operation on the East Indian Company's line at the date of the lease. On this finding and assumption the contingency on which an enhanced royalty would become payable has become operative, but it is said that this enhanced royalty is only payable in respect of coals sent over the Bengal Nagpur line and only so far as the Bengal Nagpur Railway Company charge a differential rate less than the rate charged by the East Indian Railway Company. Their Lordships cannot find any reference to such a differential rate in the terms of the clause or any support for the argument of the appellant under this head. The decision of the Subordinate Judge is rested on evidence of the intention of the parties to the deed, but this evidence is clearly inadmissible. In construing the terms of a deed the question is not what the parties may have intended, but what is the meaning of the word which they used. Apart from any question of differential rate, it is clear from the context that the words 'coals despatched in the aforesaid manner at reduced rates ' cannot be restricted as applicable only to coals sent over the Bengal Nagpur system. At the date when the lease was executed, no coals had been despatched over the Bengal Nagpur system and the deed speaks from the date of its execution. It might be argued that, grammatically, the words in question referred only to coals despatched by the East Indian Company but this construction would be adverse to the contention of the appellant. If the words in question are not limited in their application to coal despatched by the East Indian Company, they must refer back to the earlier context in the clause and include all coals despatched by rail at a reduced rate, either by the East Indian Company or the Bengal Nagpur Company. Their Lordships are of opinion that this is what the words naturally mean, and agree in the judgment of the High Court. After this judgment royalty was regularly paid at the enhanced rates of 5 annas and 2 annas 6 pies per ton until 1923. At this period Messrs. H. V. Low & Co. , Ltd. , were managing the colliery for the lessees and they had been in the habit of paying the royalty. During 1928 payment of royalties fell into arrear and on January 28, 1924, the lessee the Raja of Kasimbazar himself paid Rs. 57,069-8-0 to the lessor "in full payment of Ekra royalty from 1st January to September 30, 1923. " This payment was calculated at the enhanced rates of 5 annas and 2 annas 6 pies per ton. Messrs, Low's agency was terminated in February, 1924, and before this date Mr. F. F. Lyall, C. I. E. , I. C. S. , had been appointed manager of the Kasimbazar Estate, On March 8, 1924, Mr. Lyall wrote to the Rajah of Jharia, the lessor, stating that the rate of freight for coal had been raised on April 1, 1921, to Rs. 3-13-0; that the highest rate of royalty of 5 annas and 2 annas 6 pies per ton was "only payable on coal which may be despatched at a freight of 2 annas less than the freight which was in force at the time of the execution of the lease"; and that the lessor had been very much overpaid. He added "please note that we shall make no further payments on account of royalty until this excess is wiped out. " The lessor's manager wrote in reply "lam sorry you have put a wrong construction upon the lease and the Raja is not prepared to accept the same; the contingencies mentioned in the lease having happened, the Raja is entitled to claim the enhanced royalty for all time to come. " After some further correspondence the lessor's manager wrote to the lessees on August 18, 1924, "it is useless carrying on further correspondence as there is no chance of the matter being settled out of Court. If you think you are entitled to any refund you may sue for the same. "

(3.)THE contentions of the parties had been clearly stated. THE lessor contended that once the higher rate of royalty had come into operation, it was permanent and not affected by a subsequent rise in the rate of freight. On this view there had been no overpayment and royalties were still payable at the higher rate. THE lessee on the other hand maintained that on a true construction of the lease the higher rate of royalty was only payable on coal despatched by rail at a freight more than 2 annas below the freight at the date when the lease was entered into. On this view the higher rate of freight ceased to operate on April 1, 1921. By continuing to pay at the higher rate from that date until September 30, 1923, he had paid Rs. 63,680 more than was due, and he was entitled to retain future royalties up to this amount and thereafter to pay at the lower rates. THE lessee acted on this view of his rights. He made no further payment of royalties until August 20, 1925, and from that date onwards he continued to pay royalty at the lower rates.
The lessor protested and did not acquiesce, but he took no steps to enforce what he asserted to be his rights until he raised the present action on February 5, 1936. In view of the provision for hypothecation contained in Clause 10 of the lease the lessor, the present appellant, was able to bring his action in the form of a mortgage suit in which he claimed an account for the previous twelve years on the footing that royalty had been due throughout that period at the higher rates, and that he was entitled to interest on arrears unpaid.