A still more extensive missionary journey was undertaken at a later date, 1677, by several Quakers, among them Fox, Penn, Furly, Barclay and Keith. They visited Brill, Leyden and Haarlem where they held meetings, preaching to both Quakers and Mennonites.[22] The tour continued up into the Rhine region where Penn and his party came into touch with members of the Pietist group. It is doubtless true that this journey and the impression which was made by Penn must have played an important part a few years later when he opened his colony to settlers on the well known liberal principles. In the presentation of the foregoing material it has been pointed out: (1) how the doctrines of the Quakers were rapidly spread broadcast by the itinerant preachers; and (2) that there was a great similarity between Quaker and Mennonite in doctrine and belief. [Sidenote: Increased number of ministers] [Sidenote: The number of adherents estimated] The work of spreading the new gospel, as instanced by the work of Ames and Rolfe in 1657, was carried rapidly forward; as early as 1654, seven years after George Fox had begun to preach, he had enlisted the services of some sixty preachers who travelled continually up and down the country.[23] Such a number of leaders bespeaks a considerable following, though we have no record of a census of the followers made during Fox’s lifetime. Brown is apparently willing to accept Barclay’s statement that by 1675 they numbered ten thousand in London and by the end of the century, sixty thousand.[24] It does not seem that this is too large an estimate. It can be estimated from the work of Besse on _Sufferings_ that between 1650 and 1689 there were approximately fifteen thousand individual cases of “sufferings.”[25] Since his work is compiled from “authentic records” it may be considered to be fairly accurate, though the errors, if any, would likely be to make the number too small rather than too large. As a matter of fact his collection includes some cases between 1689 and 1700, but the vast majority of them are from the period above stated. Certainly we must suppose that if such a large number actually came under the hand of English tolerance, then the total number of adherents very probably equalled or exceeded the estimate previously mentioned. Whatever objection may be made to the accuracy of these figures they may certainly be taken as fairly indicative of the growth of the sect; for that purpose they are intended. [Sidenote: Fox’s doctrine the basis in their educational practice]