Archives July 2014

Both waterproof and airtight, cellophane is now used for everything from food packaging to sticky tape. The man who invented it—Swiss textiles engineer Jacques E. Brandenberger (1872-1954)—initially wanted to develop a clear coating for cloth to make it waterproof after witnessing a wine spill on a restaurant tablecloth. He tried coating cloth with a thin sheet of viscose, but viscose made the cloth too stiff. The transparent sheet of film separated easily from the cloth and Brandenberger soon realized that the film itself had more potential than the waterproofed cloth. To create cellophane, Brandenberger dissolved cellulose fibers from materials such as celery, wood, cotton, or hemp in alkali and carbon disulfide to make viscose, which is then extruded through a slit into an acid bath to reconvert the viscose back into cellulose. The acid regenerates the cellulose, which forms a film, and further treatment—for example washing and bleaching—produces cellophane. (Rayon more...

Spectrophotometers are used to measure the intensity of electromagnetic radiation. Usually the measurements are confined by filters to a very narrow spectral range and the instrument is used to detect the change in brightness after the light radiation has either passed through a sample or been reflected off it. Early devices used the naked eye to determine the differences in intensity between two beams. Arthur Hardy (1895-1977), a physicist at the Massachusetts Institute of Technology, decided to replace the eye with the new cesium photocells, and thus detect intensities electronically. The plan was to produce a Spectrophotometer that automatically scanned through the visible spectrum and produced a pen-drawn spectrum showing how the light intensity varied with wavelength. Beam splitters and rotating polarizers were used and the two beams were compared by blinking quickly from one to another using a flicker photometer technique. Working in collaboration with the firm General Electric, more...

"What then is time? If no one asks me, I know what it is. If I wish to explain it, ...I do not know." Saint Augustine, theologian A time zone is a longitude band around the globe in which everyone sets their clocks to the same time— regulated by the movement of the sun. Before time zones were introduced, every town kept its own local time. But with the advent of the railways this system became very inconvenient, as the time at the starting point of a journey might well differ from the one at the terminus. In 1847 the railway companies in Great Britain recommended that all docks should be set using the same time marker. Noon on the Greenwich Meridian (0 degrees longitude) was chosen, which is known as Greenwich Mean Time (G.M.T.). Because Earth spins every twenty-four hours, local time varies by one hour for every 15-degree more...

Doctors treating polio patients found that while many sufferers were unable to breathe in the acute stage, when the action of the virus paralyzed muscles in the chest, those who survived this stage usually recovered completely. Such observations indicated the need to develop strategies to maintain respiration until the patient could breathe independently again. In 1927, chemical engineers Philip Drinker (1894-1972) and Louis Agassiz Shaw, from Harvard University, devised a tank respirator to maintain respiration. In the device, the patient's head stuck out of the end of the tank, with a sponge rubber seal to make it airtight. Air was then pumped from the tank to produce negative pressure causing the chest to expand and thus produce breathing. The first iron lung was installed in 1927 at Bellevue Hospital, New York, and in 1928 the first patient was an eight-year-old girl with polio, comatosed from lack of oxygen. One minute more...

"I... have [decided to call my invention] the Improved Endless-Wire-Rope Way." Andrew S. Hallidie The first cable-operated railway was the London and Blackwall Railway, which opened in 1840. It consisted of a line 3.5 miles (5.6 km) long with hemp rope hauling the cars, but because the ropes wore out too quickly, it switched to steam locomotives in 1848. In 1870 San Francisco attorney Benjamin Brooks proposed using cable cars to provide fast, inexpensive, and convenient access to the desirable heights of that hilly city. Horsedrawn cars worked well on level ground but had great difficulty with San Francisco's steep gradients. Brooks obtained a cable-line franchise from the city but was unable to obtain financing and sold it to Andrew Smith Hallidie (1836-1900). Hallidie had been the first person in California to manufacture wire rope, and by 1871 he had two cable- car patents to his name. He hired engineer more...