"Besides this independence, Franklin was the holder of two offices, worth together perhaps one hundred and fifty pounds a year. His business, then more flourishing than ever, produced an annual profit, as before computed, of two thousand pounds; bringing up his income to the troublesome and absurd amount of nearly three thousand pounds; three times the revenue of a colonial governor." Under these prosperous circumstances, Franklin withdrew from active business, became a silent partner in the firm, and devoted nearly all his time to the new science. He wrote, in the autumn of 1748, to his friend Cadwallader Colden of New York, "I have removed to a more quiet part of the town, where I am settling my old accounts, and hope soon to be quite master of my own time, and no longer, as the song has it, 'at every one's call but my own.' "Thus you see I am in a fair way of having no other tasks than such as I shall like to give myself, and of enjoying what I look upon as a great happiness, leisure to read, study, make experiments, and converse at large with such ingenious and worthy men, as are pleased to honor me with their friendship or acquaintance, on such points as may produce something for the common benefit of mankind, uninterrupted by the cares and fatigues of business." He wrote a treatise upon thundergusts, which displayed wonderful sagacity, and which arrested the attention of nearly all the philosophers in Europe and America. The all-important topics of this exceedingly important document, were the power of points to draw off electricity, and also the similarity of electricity and lightning. He therefore urged that metallic rods might be attached to buildings and ships, which, pushing their needle points above roofs and masts, might draw the electric fire harmlessly from the clouds. He confesses that he cannot imagine why the points should possess this curious power, but urges that facts seem to demonstrate it. One day, for the entertainment of his friends, he had made arrangements to kill a turkey with an electric shock. Two large jars were heavily charged. Incautiously manipulating, he took the shock himself. In the following language, he describes the effect: "The flash was very great, and the crack was as loud as a pistol; yet my senses being instantly gone, I neither saw the one nor heard the other; nor did I feel the stroke on my hand, though I afterwards found it raised a round swelling where the fire entered, as big as half a pistol bullet.