The news of this great success quickly reached Paris, and led to many attempts to imitate and develop the striking invention. In Paris, the work was taken up by the brothers Robert, makers of scientific instruments, and Professor Charles, a young and promising physicist. They made a balloon 12 feet in diameter and filled it with hydrogen gas. It rose into the air and sailed away before a huge crowd of people. A few days afterwards, the brothers Montgolfier brought to Paris a giant balloon 72 feet high, which also rose into the air, but was held back by ropes. A week after that they attached to the balloon a car of wickerwork, in which they put a sheep, a cock, and a duck. The balloon came to the ground somewhere out in the country, and all the three animals alighted safe and sound. The success of these first three navigators of the air encouraged the human inventors of the balloon to venture themselves into cloudland, and in November of the same year two Frenchmen ascended in a fire-balloon and sailed over Paris across the river Seine. To show that the same could be done in a balloon filled with hydrogen, Charles and Robert made an ascent in a gas balloon a few days later. The balloon was made in lengths of red and yellow silk. It was provided with a net, to which the car was attached, with a valve for letting out the gas, with a barometer for measuring the height, and with bags of sand. The sand was taken as ballast, and was used to lessen the weight of the balloon when it was sinking too quickly. The great hopes built upon the balloon were not fulfilled for many years. Benjamin Franklin, when he first saw a balloon, said he had seen an infant which he hoped to see grow into a giant. But for ninety years no decided improvement was made in the construction of the balloon. Bold investigators of the air were found to cross the Channel from Dover to Calais, or from London to Germany, as Green did in 1836 in a giant balloon filled with coal-gas. Some great heights were reached. In 1862 two Englishmen named Glaisher and Coxwell rose to a height of seven miles, the greatest height ever attained by people in a balloon. Their pulses rose till they gave 110 beats per minute instead of about 70 or 80 beats per minute. Their faces became purple, and finally Glaisher became unconscious. Coxwell lost the use of his hands in the extreme cold of the upper air, but he managed to pull the valve rope with his teeth, and so they both returned safely to Mother Earth.