Among his other occupations at Cape Town, Livingstone put himself under the instructions of the Astronomer-Royal, Mr. (afterward Sir Thomas) Maclear, who became one of his best and most esteemed friends. His object was to qualify himself more thoroughly for taking observations that would give perfect accuracy to his geographical explorations. He tried English preaching too, but his throat was still tender, and he felt very nervous, as he had done at Ongar. "What a little thing," he writes to Mr. Moffat, "is sufficient to bring down to old-wifeishness such a rough tyke as I consider myself! Poor, proud human nature is a great fool after all." A second effort was more successful. "I preached," he writes to his wife, "on the text, 'Why will ye die?' I had it written out and only referred to it twice, which is an improvement in English. I hope good was done. The people were very attentive indeed. I felt less at a loss than in Union Chapel[35]." He arranged with a mercantile friend, Mr. Rutherfoord, to direct the operations of a native trader, George Fleming, whom that gentleman was to employ for the purpose of introducing lawful traffic in order to supplant the slave-trade. [Footnote 35: The manuscript of this sermon still exists. The sermon is very simple, scriptural, and earnest, in the style of Bishop Ryle, or of Mr. Moody.] It was not till the 8th of June that he left the Cape. His wagon was loaded to double the usual weight from his good nature in taking everybody's packages. His oxen were lean, and he was too poor to provide better. He reached Griqua Town on the 15th August, and Kuruman a fortnight later. Many things had occasioned unexpected delay, and the last crowning detention was caused by the breaking down of a wheel. It turned out, however, that these delays were probably the means of saving his life. Had they not occurred he would have reached Kolobeng in August. But this was the very time when the commando of the Boers, numbering 600 colonists and many natives besides, were busy with the work of death and destruction. Had he been at Kolobeng, Pretorius would probably have executed his threat of killing him; at the least he would have been deprived of all the property that he carried with him, and his projected enterprise would have been brought to an end. In a letter to his wife, Livingstone gives full details of the horrible outrage perpetrated shortly before by the Boers at Kolobeng: