D O C . 1 2 4 O C T O B E R 1 9 1 9 1 0 7 given a visa directly (2) that notification of authorization be made by telegram to Berlin. —So you should be receiving the report about the entry permit very soon. Please then telegraph me when you are coming. And once again: arrange the whole trip so that you are strained as little as possible and don’t save money on that.— N.B. Take only very little Dutch money with you—just enough to come to Leyden. I am enclosing another more official letter, in case it is needed. Affect. greetings! Until our imminent happy reunion, yours, P. Ehrenfest The children are expecting you with impatience. Shall we be able to make music together as well? I play much better now than formerly! 124. From Paul Ehrenfest Leyden, 5 October 1919 Highly esteemed Colleague, In renewing my invitation, I would also like to inform you that it would be very desirable that you come here as early as possible in October, because toward the end of October and, altogether, later still it would be extremely difficult for a few of our colleagues, who would like to confer with you regularly partly about questions on gravitation and partly on quanta, to come to Leyden from various uni- versity towns. We shall wait with the precise fixing of the date on which you should give your lecture until we receive your reply however, the week from 13–18 Octo- ber would be most favorable. Alternatively, the week of 20–25 October. As it is of great importance to us all that you come directly, Professor Kamerlingh-Onnes has requested of the Passport Center in The Hague that your en- try be approved immediately and the authorization be relayed by telegram to Ber- lin. We consequently hope that you can be in Leyden already on the 13th. Notifica- tion by telegram about when you will be arriving at the border is requested. Together with all my fellow specialists in this country, I remain in happy anti- cipation of your arrival. With sincere respect, yours, P. Ehrenfest Prof. Lorentz apparently also wrote you a few days ago.