A microscope is an instrument used to see objects that are too small to be seen by the naked eye. Microscopy is the science of investigating small structures using such an instrument. Microscopic means invisible to the eye. There are many types of microscopes, they may be grouped in different ways. One way is to describe the way the instruments interact with a sample to create images, either by sending a beam of light or electrons to a sample in its optical path, or by scanning across, a short distance from the surface of a sample using a probe; the most common microscope is the optical microscope, which uses light to pass through a sample to produce an image. Other major types of microscopes are the fluorescence microscope, the electron microscope and the various types of scanning probe microscopes. Although objects resembling lenses date back 4000 years and there are Greek accounts of the optical properties of water-filled spheres followed by many centuries of writings on optics, the earliest known use of simple microscopes dates back to the widespread use of lenses in eyeglasses in the 13th century.
The earliest known examples of compound microscopes, which combine an objective lens near the specimen with an eyepiece to view a real image, appeared in Europe around 1620. The inventor is unknown. Several revolve around the spectacle-making centers in the Netherlands including claims it was invented in 1590 by Zacharias Janssen and/or Zacharias' father, Hans Martens, claims it was invented by their neighbor and rival spectacle maker, Hans Lippershey, claims it was invented by expatriate Cornelis Drebbel, noted to have a version in London in 1619. Galileo Galilei seems to have found after 1610 that he could close focus his telescope to view small objects and, after seeing a compound microscope built by Drebbel exhibited in Rome in 1624, built his own improved version. Giovanni Faber coined the name microscope for the compound microscope Galileo submitted to the Accademia dei Lincei in 1625; the first detailed account of the microscopic anatomy of organic tissue based on the use of a microscope did not appear until 1644, in Giambattista Odierna's L'occhio della mosca, or The Fly's Eye.
The microscope was still a novelty until the 1660s and 1670s when naturalists in Italy, the Netherlands and England began using them to study biology. Italian scientist Marcello Malpighi, called the father of histology by some historians of biology, began his analysis of biological structures with the lungs. Robert Hooke's Micrographia had a huge impact because of its impressive illustrations. A significant contribution came from Antonie van Leeuwenhoek who achieved up to 300 times magnification using a simple single lens microscope, he sandwiched a small glass ball lens between the holes in two metal plates riveted together, with an adjustable-by-screws needle attached to mount the specimen. Van Leeuwenhoek re-discovered red blood cells and spermatozoa, helped popularise the use of microscopes to view biological ultrastructure. On 9 October 1676, van Leeuwenhoek reported the discovery of micro-organisms; the performance of a light microscope depends on the quality and correct use of the condensor lens system to focus light on the specimen and the objective lens to capture the light from the specimen and form an image.
Early instruments were limited until this principle was appreciated and developed from the late 19th to early 20th century, until electric lamps were available as light sources. In 1893 August Köhler developed a key principle of sample illumination, Köhler illumination, central to achieving the theoretical limits of resolution for the light microscope; this method of sample illumination produces lighting and overcomes the limited contrast and resolution imposed by early techniques of sample illumination. Further developments in sample illumination came from the discovery of phase contrast by Frits Zernike in 1953, differential interference contrast illumination by Georges Nomarski in 1955. In the early 20th century a significant alternative to the light microscope was developed, an instrument that uses a beam of electrons rather than light to generate an image; the German physicist, Ernst Ruska, working with electrical engineer Max Knoll, developed the first prototype electron microscope in 1931, a transmission electron microscope.
The transmission electron microscope works on similar principles to an optical microscope but uses electrons in the place of light and electromagnets in the place of glass lenses. Use of electrons, instead of light, allows for much higher resolution. Development of the transmission electron microscope was followed in 1935 by the development of the scanning electron microscope by Max Knoll. Although TEMs were being used for research before WWII, became popular afterwards, the SEM was not commercially available until 1965. Transmission electron microscopes became popular following the Second World War. Ernst Ruska, working at Siemens, developed the first commercial transmission electron microscope and, in the 1950s, major scientific conferences on electron microscopy started being held. In 1965, the first commercial scanning electron microscope was developed by Profess
HMS Ruby was a 64-gun third-rate ship of the line of the Royal Navy, launched on 26 November 1776 at Woolwich. She was converted to serve as a receiving ship in 1813 and was broken up in 1821; the British ships Ruby, Captain Michael John Everitt, Aeolus, 32, the sloop Jamaica, 18, were cruising off Hayti, when on 2 June 1779, in the Bay of Gonave, they fell in with the 36-gun French frigate Prudente, Captain d'Escars. Ruby chased Prudente for some hours and was much annoyed by the well-directed fire of the enemy's stern-chasers, by which Captain Everitt and a sailor lost their lives; when within easy range of Prudente, at about sunset, Ruby compelled her to strike, with the loss of two killed and three wounded. The British Navy took Prudente into service under the same name. HMS Ruby sailed with the first squadron to take part in the 1st British Occupation of the Cape, leaving England on 27 February 1795. There she saw no action; the Battle of Muizenberg on 7 August 1795 triggered the collapse of the Dutch forces which controlled the Cape of Good Hope at the time.
Media related to HMS Ruby at Wikimedia Commons
International Bridge Walk is an annual event held on the last Saturday in June where participants can walk from Sault Ste. Marie, Michigan, to Sault Ste. Marie, via the International Bridge. Begun in 1987, it represents the friendship between the two Saults and both countries, is held in conjunction with Canada's national holiday, Canada Day; the walk begins at the Norris Building parking lot of Lake Superior State University with speeches from officials of both Saults and the singing of "O Canada" and "The Star Spangled Banner". Participants begin walking about 9:00 a.m. and proceed west on Easterday Avenue and to the on-ramp near the bridge's toll plaza and finish at the OLG Casino west parking lot in Canada. Buses are provided for U. S. citizens to return to the U. S; the walk concludes at 10:30 a.m. and no one can walk the bridge after that time. In 2012, a bicycle parade was added to the annual event to cross the bridge from 8:30 to 9:30, the walk now taking place from 9:30 to 11:00. International Bridge Administration