tank. When the weight of the water in the scoop filled to an excess, it overcame a counterweight that in turn tripped a lever allowing the scoop to rotate on a pivot and drain its water. However, as the scoop fell, it tripped a coupling tongue that temporarily pulled down on a long vertical chain, the latter yanking down on a balancing lever which would pull upward on a small chain connected to a locking arm, the latter lifting momentarily to release the top arrested spoke before coming back down to repeat the entire process over again. It should be pointed out that the Chinese intermittently working liquid-driven escapement had "only the name in common" with the true mechanical escapement of medieval European mechanical clocks of the 14th century onwards, which worked instead with weights, producing continuous but discrete beats and that derived from the Greek and Roman verge mechanism (alarum) device of earlier mechanisms. Exploding cannonballs: The Huolongjing military manual compiled by the Ming dynasty military official Jiao Yu (fl. 14th to early 15th century) and the Ming dynasty military strategist and philosopher Liu Bowen (1311–1375) in the mid 14th century described the earliest known exploding cannonballs, which were made of cast iron with a hollow core packed with gunpowder. Jiao and Liu wrote that when fired, they could set enemy camps ablaze. The earliest evidence for exploding cannonballs in Europe date to the 16th century. The Huolongjing also specified the use of poison and blinding gunpowder filled into exploding shells; the effects of this chemical warfare was described as such: "Enemy soldiers will get their faces and eyes burnt, and the smoke will attack their noses, mouths, and eyes." F Field mill: In the Yezhongji ('Record of Affairs at the Capital Ye of the Later Zhao Dynasty') written by Lu Hui (fl. 350 AD), various mechanical devices are described which were invented by two Later Zhao (319–351) engineers known as Xie Fei, a Palace Officer, and Wei Mengbian, the Director of the Imperial Workshops. One of these is the field mill, which was essentially a cart with millstones placed onto the frame; these were mechanically rotated by the movement of the cart's terrain wheels in order to grind wheat and other cereal crops. A similar vehicle these two invented was the "pounding cart", which had wooden statues mounted on the top which were actually mechanical figures who operated