DEAR BOY: I have received your letter of the 12th, N. S., in which I was surprised to find no mention of your approaching journey to Berlin, which, according to the first plan, was to be on the 20th, N. S., and upon which supposition I have for some time directed my letters to you, and Mr. Harte, at Berlin. I should be glad that yours were more minute with regard to your motions and transactions; and I desire that, for the future, they may contain accounts of what and who you see and hear, in your several places of residence; for I interest myself as much in the company you keep, and the pleasures you take, as in the studies you pursue; and therefore, equally desire to be informed of them all. Another thing I desire, which is, that you will acknowledge my letters by their dates, that I may know which you do, and which you do not receive. As you found your brain considerably affected by the cold, you were very prudent not to turn it to poetry in that situation; and not less judicious in declining the borrowed aid of a stove, whose fumigation, instead of inspiration, would at best have produced what Mr. Pope calls a souterkin of wit. I will show your letter to Duval, by way of justification for not answering his challenge; and I think he must allow the validity of it; for a frozen brain is as unfit to answer a challenge in poetry, as a blunt sword is for a single combat. You may if you please, and therefore I flatter myself that you will, profit considerably by your stay at Berlin, in the article of manners and useful knowledge. Attention to what you will see and hear there, together with proper inquiries, and a little care and method in taking notes of what is more material, will procure you much useful knowledge. Many young people are so light, so dissipated, and so incurious, that they can hardly be said to see what they see, or hear what they hear: that is, they hear in so superficial and inattentive a manner, that they might as well not see nor hear at all. For instance, if they see a public building, as a college, an hospital, an arsenal, etc., they content themselves with the first 'coup d'oeil', and neither take the time nor the trouble of informing themselves of the material parts of them; which are the constitution, the rules, and the order and economy in the inside. You will, I hope, go deeper, and make your way into the substance of things. For example, should you see a regiment reviewed at Berlin or Potsdam, instead of contenting yourself with the general glitter of the collective corps, and saying, 'par maniere d'acquit', that is very fine, I hope you will ask what number of troops or companies it consists of; what number of officers of the Etat Major, and what number of subalternes; how many 'bas officiers', or non-commissioned officers, as sergeants, corporals, 'anspessades, frey corporals', etc., their pay, their clothing, and by whom; whether by the colonels, or captains, or