A mail route from Montreal into Upper Canada was also established, but this was rather a military post, intended to serve the military stations and frontier settlements. The mail was despatched only once a year and was, in consequence, known as the "yearly express." The route followed was by the St. Lawrence from Montreal to Matilda, Augusta, and Kingston; across Lake Ontario to Niagara; thence to Detroit Fort, at the base of Lake St. Clair, and across Lake Huron to Michilimackinac, at the head of Lakes Huron and Michigan. After continuing some six years this post was curtailed and went no farther than Niagara.[108] In 1800 Finlay was succeeded in the deputy ship by John Heriot. The population had now increased to 450,000, but there were only twenty post offices in the whole of the five provinces. Heriot's patent gave him authority to establish new routes and offices, but, in accordance with the general policy, only when in his opinion their establishment would be likely to benefit revenue. The rates at this time were, of course, nominally based on the Act of the 5th George III, but as the routes had never been properly measured, the distances on which the rates were actually based were largely a matter of conjecture. The posts were said, however, to have paid their way and even to have yielded a surplus revenue, which was transmitted to England.[109] The administration of the posts rested ultimately with the Postmasters-General in London. The service could be extended only by their authority, and the colonists found that the Deputy in the colonies, being bound by his instructions from the Postmasters-General, was unable to extend and improve the service in the manner which they themselves thought desirable. A large number of immigrants entered the provinces, especially Upper Canada, during this period, and settlements were springing up in remote districts far away from the post routes. Heriot was admonished from London that in considering the provision of new services he must look to the revenue to be anticipated as well as to the convenience of the public, and to adopt no scheme involving sacrifice of revenue. His instructions forbade the opening of any post office or post route unless the anticipated revenue was sufficient at least to pay the postmaster and courier. He found that these restrictions prevented him from providing a service in any degree adequate to the demands of the settlers, or indeed adequate to their real needs. It was essential that the settlers in the remote districts should be kept in touch with civilization. They could not be allowed to pass beyond the reach of the Government. They must be kept in contact with the means provided for the administration of the law. For these reasons it was essential to provide post accommodation, although in the nature of the case it could not be expected that a revenue sufficient to cover the cost would be obtained. All these considerations were pressed