History of chemistry iodine first, but both scientists acknowledged Courtois as the first to isolate the element. In 1815, Humphry Davy invented the Davy lamp, which allowed miners within coal mines to work safely in the presence of flammable gases. There had been many mining explosions caused by firedamp or methane often ignited by open flames of the lamps then used by miners. Davy conceived of using an iron gauze to enclose a lamp's flame, and so prevent the methane burning inside the lamp from passing out to the general atmosphere. Although the idea of the safety lamp had already been demonstrated by
Slit lamp retina. Two conflicting trends emerged in the development of the slit lamp. One trend originated from clinical research and aimed to apply the increasingly complex and advanced technology of the time. The second trend originated from ophthalmologic practice and aimed at technical perfection and a restriction to useful methods. The first man credited with developments in this field was Hermann von Helmholtz (1850) when he invented the ophthalmoscope. In ophthalmology and optometry, the instrument is called a "slit lamp", although it is more correctly called a "slit lamp instrument". Today's instrument is a combination of two separate developments, the corneal