MATHER, Sarah, American. Inventor of a deep-sea telescope of an imaginative technical design (which was later improved upon by her daughter). The device, which was much used, permitted inspection of the hull from above the water. Known obstructions were monitored and it was used to survey wrecks, it even helped spot torpedoes and underwater craft. A lamp was also incorporated into the device. In 1845 this was a most valuable marine development.