Great advances in glass manufacture take place such as perfection of the earliest optical lenses to block the harmful ultraviolet rays of the sun and improvements in lighthouse illumination. The company is responsible for glazing the original Crystal Palace to house the Great Exhibition of 1851, and the Houses of Parliament (built 1840–1860). At that time it is the only firm that is able to make the opal glass for the four faces of the Westminster Clock Tower that houses the famous bell, Big Ben. The ornamental windows for the White House in America are also made at Chances. 1832: A form of German silver is invented by Charles Askins, this is used to make spoons and cutlery specifically in the Birmingham area. 1837: Bird's Custard is first formulated and cooked by Alfred Bird, because his wife is allergic to eggs, the key ingredient used to thicken traditional custard. Bird's custard powder later becomes famous around the world. 1838: Charles Green patents an original and unique method of producing solid, seamless brass and copper tubes, around this time much development takes place in Birmingham and Manchester with regard to copper tubing and printing plates. 1839: After many years of research, innovation and campaigning, Rowland Hill (of Kidderminster and later Birmingham) is given a two-year contract to run his new postal system. Hill is an English teacher, inventor and social reformer. He campaigns for a comprehensive reform of the postal system, based on the concept of penny postage and his solution of prepayment facilitates the safe, speedy and cheap transfer of letters. Hill later serves as a government postal official, and he is usually credited with originating the basic concepts of the modern postal service, including the invention of the postage stamp (his brother Edwin Hill helps the service with further innovations). 1839: Sir Edward Thomason improves the gun lock by making the cock detachable by the thumb and finger as well as making improvements to prevent misfires. George Elkington and Henry Elkington found the English electroplating industry in the early 19th century. In 1840, they aid John Wright, who discovers that potassium cyanide is a suitable electrolyte for gold and silver electroplating. Carl Wilhelm Siemens has several meetings with George Elkington, and makes speeches on 'Science and Industry,' to the Birmingham and Midland Institute, he later sets up a works in Birmingham and carries out experiments on metals and telegraphy.