The critics who oppose, Say, mention that Say’s law of markets can only be applied in one industry or firm and is not applicable on the whole economy as desired. For example, as a result of over-production in the industry there will be unemployment and hence rewards to factors of production will be cut down, under free competition. Cost of production will be going down and as a result prices of the products will go down too. Hence, there will be excess demand for goods and services and over-production will be eliminated. But this is possible only in case of an industry. However Say’s theory is not applicable on the economy as a whole because as a result of the low prices of the products the aggregate demand cannot be increased and hence over production will continue and unemployment will persist.

According to J.B. Say himself, prices of goods are highly flexible at the full employment level due to which the aggregate supply of the goods adjusts with the aggregate demand for it and therefore, eliminates the possible signs of over-production and unemployment. However, in the real world, today, prices of goods and services are generally stable. Hence, in case of absolute prices, over production cannot be eliminated and consequently unemployment takes place.

Say’s theory is explained with reference to the circular flow of national income; according to which people living in a country are in the aggregate sense, the producers as well as the ultimate consumers, Consequently, over production does not take place. For example, we already know that people get their rewards in the form of rent, interest, wages and profits respectively by which they create demand for the aggregate supply of goods and services. Now in reality, demand for consumer goods takes place immediately but the demand for capital goods takes some time to be initiated as the people would generally think first about their investment projects. As a result of this time lag, over-production and unemployment can take place.

The cutting and polishing of diamonds are very delicate operations that can be carried out only by skilled craftsmen who pass on their art from one generation to the next.

Not all diamonds can be cut and transformed into elegant stones. The more impure ones and fragments obtained from cutting gems are used in industry. Diamonds are extremely hard and are valuable in cutting or polishing the hardest of metallic alloys.

Another precious stone that is extremely rare and very valuable is the emerald which is a beautiful green color. Emeralds are usually small. When one is larger than ten carats and free from impurities and faults it is much more valuable than a diamond of the same size.

Much of the value of these gems depends on the way they have been cut. The usual way is to cut surfaces or facets on them so that they will refract or break up the light that passes through the stone. The effect is to produce a number of small prisms which break up the light into the beautiful flashing colors of the rainbow. Great skill is necessary at every stage of diamond cutting, but especially during faceting, as the angles of the facets must be exact to give the maximum amount of brilliance and to preserve the symmetry of the stone. The upper part of the faceted gem is called the crown and the lower is called the base or pavilion.

Erosion is a constant natural process by which rocks are worn away. This process is affected by the amount of rainfall and the strength and direction of the wind.

Sometimes the effects of erosion are so weird and wonderful it seems as if a magician has been at work. Some of the strangest effects can be seen in pyramids which resemble a series of pinnacles each surmounted by a rock.

These pyramids are the result of the softer underlying material being worn away while the harder rock act as an umbrella and protect the soil underneath from the attacks of rainfall. These rocks mark the former level of the ground before it was worn away by erosion.

The most famous of these formations include those in Monument Valley in Utah in the United States.

To establish how effective a drug is it must be tested carefully and accurately and its effect on living organism meticulously studied and noted. This is the task of pharmacology, a science which has made tremendous advance in less than a century.

The work of pharmacologists is often related to biochemistry, since they study the effects of foreign substances on cells or chemical systems of the body; and to psychiatry, for they also study the effects of drugs on the brain and behavior.

The most significant stage in the discovery of a new drug is when the active substance that has curative properties is isolated. These substances are then checked for the effect they have on living tissues. This could be dangerous on a human being and even the curative properties of any drug can prove fatal if they are administered in wrong doses.

To overcome these difficulties scientists carry out their experiments on animals such as dogs, cats, mice, guinea pigs, rabbits and monkeys. Many such animals are sacrificed daily in the laboratories of the world, although most countries have strict laws which forbid the infliction of unnecessary pain on them.

One of the most common experiments is to infect these animals with germs to develop diseases. Sometimes various organs are removed from these laboratory animals for detailed study of their functions.