Letter from Donald McLean, to the Honble, the Colonial Secretary, dated 1st. June 1850. relating to payment of the Second Instalment of Rangitikei purchase. Wellington, June 1st. 1850. Sir, I have the honor to acknowledge the receipt of your letter of yesterday's date, in reference to the difficulty that has arisen in supplying the amount of the Second Instalment for the Rangitikei purchase; and instructing me