, of Alexandria, a famous mathematician about 120 years B. C. was, it is reported, the first inventor of the pump, which he discovered by accident. On lowering a mirror that was in his father’s shop, he observed that the weight which helped it in moving upwards and downwards, and which was inclosed in a cylinder, made a noise, produced by the friction of the air violently forced by the weight. He set about examining into the cause of this sound, and thought it might be possible to avail himself of it in making an hydraulic organ, in which the air and the water should form the sound; an undertaking which he executed with success. Encouraged by this production, Ctesibius thought of using his mechanical skill in measuring time. He constructed a clepsydra, or waterclock, formed with water, and regulated by cogged wheels; the water by falling turned these wheels, which communicated their motion to a column on which were marked the characters for distinguishing the months and the hours. At the same time that the cogged wheels were put in motion, they raised a little statue, which with a wand pointed to the months and hours marked upon the column. He was also the author of “Geodesia, or the art of dividing and measuring bodies,” which is said to be in the Vatican library; but he must be distinguished from Ctesibius of Chalcis, who was a cynic philosopher, of a sportive disposition and a cheerful temper, who had the art of being agreeable to the great, without submitting to the vile arts of flattery, and made them hearken to truth, and gave them a taste for virtue, under the name of amusement. 2