256) _____ asserted that science depends upon observation of facts.

257) The English Physician, _____ discovered how blood circulates from the heart through arteries to different parts of the body and comes back to the heart through veins.

258) The invention of Gun Powder by ......revolutionized the art of warfare and became an important factor for the beginning of modern period

259) The _____, was an instrument which indicated direction and helped the daring navigators, who explored new lands which later changed the very face of the Earth.

260) _____ is the name given to the great religious revolt of the 16th century, which permanently divided the Christendom into great sects.