Archives March 2013

Last Sunday, I got up early in the morning. It was about 5 0' clock. Some of my friends came to my home. We all went to the river side for a long walk. It was a very pleasant time. Nature was at her best. A cool breeze was blowing. Birds were singing soft, sweet notes. Dew drops on the grass looked like pearls. Everything was green and fresh. We enjoyed swimming in the river and came back at about eight. I then had my breakfast. After this, I did my home task and prepared my  lesson. It took me about three hours. It was almost noon. I had my usual meal. After this, I enjoyed a nap for some time. I got up at about 1 p.m. The sky was overcast with clouds and the weather was very pleasant. For some time, I played cards with my younger brothers more...

In 1815 the Tambora volcano in Indonesia erupted, starting a chain of events that led to the invention of the bicycle. The eruption was the largest in recorded history and dumped tons of ash into Earth's atmosphere. This caused the global temperature to drop, and did terrible things to crops. Three years earlier, following some bad weather in 1812, the price of oats was climbing, and the German inventor Karl Drais (1785-1851) was looking for something to replace hungry horses. He designed a four-wheeled vehicle, powered by a servant sitting in the back pedaling, while the master steered from the front with a tiller. It did not catch on and Drais decided to focus instead on surveying equipment. After the 1815 volcanic eruption, even worse weather caused oat prices to climb higher still. The need for horseless transport was even more pressing, and so Drais tried again. He switched from more...

The term internal combustion engine tends to refer to reciprocating piston engines in which combustion is intermittent, although continuous combustion engines, such as jet engines, rockets, and gas turbines are also internal combustion engines. In the seventeenth century, Sir Samuel Morland, an English inventor, used gunpowder to drive water pumps, creating the first rudimentary internal combustion engine, but it was not until 1794 that Robert Street actually built a compressionless engine. In 1879 Karl Benz designed and built the four-stroke engine that powered the first automobiles. The most significant distinction between modern internal combustion engines and the early designs is the use of in-cylinder compression. The first internal combustion engines did not have compression, but ran on an air, fuel mixture sucked in during the first part of the intake stroke. Within the internal combustion engine, the combustion of fuel and an oxidizer (normally air) occurs in confined spaces, the more...

An instrument designed for measuring horizontal and vertical angles, the theodolite is of critical importance to the surveying profession. Comprising a telescopic lens that can tilt on both horizontal and vertical axes, the theodolite is essential in "triangulation," a long- established technique for surveying tracts of land. The distance between two points is measured, to become the baseline of a triangle. The theodolite is placed at one end of the line and used to determine the angle to a predefined distant point (which makes the third corner of the triangle). The instrument is then moved to other end of the baseline, where a second angle is measured to that same point. Simple trigonometry is then employed to calculate accurately the length of the other two sides. The word theodolite first appears in a surveying textbook, A Geometric Practice Named Pantometria (1571) by mathematician and scientist Leonard Digges. Although tools for more...

“... with enough ingenuity, one could tickle the crystal with a cat's whisker and pick up anything" Theodore H. White, journalist, historian, and author Greenleaf Pickard (1877-1956) was a pioneer in the early days of wireless. He experimented with methods of receiving radio signals, using mineral crystals to filter out noise in the signal. After testing more than 30,000 combinations of materials, he finally patented his "crystal detector" in 1906. This featured a crystal of silicon that was later connected to the radio circuit via a fine, sharp piece of wire known as a cat's whisker. A crystal set radio is the simplest form of radio as it needs no power source to receive signals. A typical set consists of an antenna, a detector, a tuner, and an audio output—normally an earpiece. The antenna can be any piece of wire or metal. As radio waves pass through the antenna, tiny more...

The mass spectrometer sorts ionized atoms emitted by specific heated substances according to their individual masses. The analysis is usually performed by passing these ions through a vacuum chamber placed in a strong magnetic field. The path of individual ions is a function of their mass, velocity, and charge. The foundation of the technique was the investigation of the ions produced by cathode ray tubes, research that led to the discovery of isotopes by J. J. Thomson in 1913. An effective mass spectrometer was produced after World War I by Arthur J. Dempster (1886-1950), who used an electrical collector in 1918 at the University of Chicago. One year later Francis W. Aston (1877-1945) used a photographic plate as a detector at the University of Cambridge. Aston discovered 212 naturally occurring isotopes, and was awarded the Nobel Prize for Chemistry in 1922. By the 1940s mass spectrometers were being commercially manufactured more...

"Whose arrows are sharp, and all their bows bent, their horse's hoofs shall be counted like flint...." Isaiah 5:28 Evidence of the early use of bows and arrows has been found in cave paintings in Western Europe and North Africa. Its development probably arose in the Upper Paleolithic (Old Stone Age) around 20,000 B.C.E., when people realized that the weapon would enable hunters to kill outside their throwing range. Bows and arrows were portable, easy to make, and the materials to make them were relatively easy to obtain. The bow consisted of a thin flexible shaft of wood; this was bent, and a length of sinew, deer gut, plant fiber, or rawhide was strung tightly between its ends. Sometimes the bowstring was twisted to make it stronger. Ash, mahogany, and yew were all used for bows. Sometimes the wood was backed with sinew to make the bow stronger and stop more...

“... my own opinion is that the [Pantheon's] name is due to its round shape, like the sky." Cassius Dio, History of Rome (c. 220) Domes, like arches, present problems for architects and engineers: They remain unstable until the final stone is put in place and have to support their own weight without collapsing. It was the Romans who in circa 100 first solved these technical problems when they managed to build a true dome, that is, an unsupported half-sphere. The greatest of these is the Pantheon in Rome, which was erected in circa 123. Roman engineers tackled the problem as if it was a series of circular barrel vaults, or arches, arranged in a circle across a central point, and used concrete as a building material, in this case a mixture of lime, pumice, pieces of rock, and volcanic ash. A template for each arch was erected on scaffolding more...

"The moldboard plow... buries almost all the old crop stubble,  straw, and residue..." Rick Kubik, farm safety expert The simple moldboard plow was one of the most significant developments in history, but the name of its inventor is lost in time. When humans first began tilling their fields, they would simply drag a stick or a hoe through the soil. The resulting furrows were perfect for planting seeds for cultivation. Once humans had domesticated the ox, around 7000 B.C.E., they were able to harness its pulling power to increase plowing efficiency. The oxen pulled a hoe contained by a wooden frame. But the real breakthrough occurred in the third century B.C.E. when the Chinese designed the kuan, or moldboard plow. This consisted of a hitch, to attach it to an animal, and an asymmetric moldboard blade, which cut through the earth horizontally, with the added benefit of slicing through the more...

I read in Jain Higher Secondary School. It is not a Government School. It gets aid from the Government. Our school is built in the open. It is far from dust, noise and smoke of the city. Its building is very grand. It has verandah on both sides of the class rooms. Near the gate there are two small gardens which have grassy lawn, flower beds, fruits, trees and a beautiful fountain. We enjoy the sweet- smell of flowers and the dance of beautiful butterflies. The class rooms are very spacious having a good number of windows and ventilators. Our school has two labs, one is Physics lab and the other is Chemistry lab and a big library and a spacious reading room. Our library is full of books on all subjects. Every student can borrow books from the library. In the labs we do experiments with the help of more...