From New York to New-Haven, and thence to Boston. On the third day of April, A. D. 1850, Professor Johnston leaves, for the last, as well as only time, we trust, the shores of America, for England. We owe an apology to the reader for spending so much time upon a subject so little to our taste as the one we have presented; but as we, in common with our agricultural and horticultural friends, had expected something in our own line, from one who made high pretensions while here to instruct us in things both new and important, we have noticed his book but to chronicle another instance of the sounding brass and tinkling cymbal that so often greet us from our "Cis-Atlantic" teachers. We have done it also as a thorough confirmation of the fact that a foreigner in "getting up" a book of travels on America, has but to "steam" it across the Atlantic, trundle a thousand or two miles over our railways, gather up half-a-dozen Champagne baskets of travels, pamphlets, official reports of Legislatures, and societies - this last not much matter what - hold a conversation now and then with an ostler, tide-waiter, or barkeeper, "steam" it home again with all possible despatch, and become a most accomplished "professor" of book-making on America! Jeffreys.