Sarah Mather

Sarah Mather (fl. 1840s–1860s) was an American inventor best known for developing an early submarine telescope, a device that enabled visual inspection of submerged objects without the need for diving or dry docking. Her invention contributed to advancements in both commercial and military maritime practices and was one of the earliest documented underwater observation technologies. Mather was among the few women in 19th-century America to be granted a United States patent for a technological invention, making her an early figure in the history of women in science and engineering.

Sarah Mather lived in Brooklyn, New York, during the mid-19th century. Although detailed biographical information about her life is scarce, she is known to have been active as an inventor during a period when women were largely excluded from formal scientific and technical institutions. Social and legal constraints of the time made it difficult for women to be acknowledged as inventors, and most patents were filed by men.

There is also evidence that Mather worked closely with her son, who co-filed a later improvement patent with her in 1864. This collaboration suggests that her inventive work may have taken place within a family context that supported technological experimentation, which was one of the few avenues available to women innovators of her era.

On November 16, 1845, Sarah Mather was awarded U.S. Patent No. 3,230 for an invention officially titled the Instrument for Examining the Bottom of Ships. The invention, commonly referred to as a submarine telescope, was designed to allow shipowners and naval personnel to inspect the submerged sections of a ship’s hull without removing the vessel from the water or sending a person underwater.

The device consisted of a long, tapered metal tube that was watertight and could be lowered vertically into the water. At the submerged end, a glass viewing plate was sealed in place to allow light and visibility while keeping water out. Inside the tube, Mather installed a camphene lamp, which produced a bright flame that illuminated the area being viewed. The use of internal lighting was particularly innovative, as it enabled observation in dark or murky waters—conditions that frequently hindered underwater inspection.

This invention addressed a pressing need in the shipping industry: the ability to conduct efficient and safe maintenance of ships without expensive and time-consuming dry docking. Hull damage, marine growth, and sabotage were common concerns, and Mather’s invention provided a non-invasive, cost-effective method to detect these issues.

Although originally developed for commercial maritime purposes, the submarine telescope quickly proved relevant in military applications, especially during the American Civil War. The war brought new challenges to naval warfare, including the use of underwater mines, referred to at the time as torpedoes. Ship sabotage and blockades also became widespread tactics.

During this period, the ability to discreetly inspect the underside of a vessel became a strategic necessity. Mather’s device could be used to check for damage from underwater attacks or to detect submerged threats in harbors and rivers. It provided a tactical advantage for both ship crews and harbor defenses.

In 1864, nearly two decades after her original patent, Mather filed an improvement patent in collaboration with her son. Although the exact modifications are not extensively detailed in public records, the improved design likely included refinements to the lighting mechanism, structural durability, or portability of the device. The fact that the invention was still in development and use highlights its ongoing relevance to both civilian and military maritime needs.

Sarah Mather’s submarine telescope was a foundational step in the evolution of underwater observation technology. Her design incorporated key features—such as waterproof optics, internal illumination, and safe surface-based observation—that would later become standard in tools like periscopes, bathyscopes, and diving helmets with viewing ports. In the 20th and 21st centuries, similar principles are employed in underwater cameras, inspection systems, and remotely operated vehicles (ROVs) used in naval operations, marine biology, archaeology, and underwater construction.

Despite her contribution to early marine technology, Mather remains a relatively obscure figure in scientific history. Her presence in reference materials and historical records is limited. The achievements of women innovators—particularly those working before the 20th century—have been overlooked or minimized.

In recent years, efforts to diversify historical narratives and highlight underrepresented inventors have brought renewed attention to figures like Mather.