Monthly Archives: April 2002

Henry Cavendish


      Today’s VERITAS is a short biography of one of the greatest Scientists of all time. A person who did Science for knowledge and knowledge only. A person whose character comes closest to the picture that most people have of Scientists: uncommunicative, absent minded ….

This is the story of Henry Cavendish. And he lived in a time when Chemistry meant blasts in laboratories, smelling all sorts of pungent fumes etc.

      Cavendish was the son of Lord Charles Cavendish( one helluva rich dude). He was born on October 10 , 1731. He joined Cambridge University in 1749… but he left Cambridge without completing his degree in 1753.

After a tour of Europe he went to live in London. There he lived a frugal life and did not socialize much. His energies were devoted to the study of the Sciences.

       Cavendish had inherited a HUGE amount of wealth from his father and uncles and was one of the richest men in England. So he did not work. He only did Science( what a life!). He built a laboratory for himself and did some very important experiments.

      His earliest researches were in Chemistry and Heat. BUt his first research paper did not come until 1766. He was 35 years old when this happened. Please note that most modern “Scientists” start publishing papers when they are about 26 years old and publish a lot. Cavendish did not care much about publication and did Science to satisfy his own curiosity.

      His first paper dealt with Facticious Airs( chemical compounds). He had studied the properties of gases very carefully and had characterized them for the first time by Specific Gravity.

      In 1781 Cavendish was the first to show that when Oxygen and Hydrogen are burnt together water is formed.

He writes in his paper :

  ” …on applying the lighted paper to the mouth of the bottle… With 3 parts of inflammable air to 7 of common air, there was a very loud noise”.

  ” By the experiments it appeared that when inflammable and common air are exploded in proper proportion, almost all of the inflammable air and near one-fifth of the common air loose their elasticity and are condensed into dew”

He discovered Nitric Acid in 1795.

      Canvendish was also interested in Electric Phenomenon and spent several years experimenting with electricity. But he published only 2 papers on this subject: in 1772 and 1776. About a 100 years later Maxwell published the unpublished investigations of Cavendish. It seems that Cavendish had done the experiments that made Faraday and Coloumb famous much before them. He had just not bothered to publish. 

He discovered the composition of Air. He established through accurate experiments that Air consists of 79.167 % phlogisticated air( now nitrogen + argon) and 20.833% dephlogisticated air( now known as oxygen). He also established that 1/120 of air is a third gas( now we know that this is CO2).

    Cavendish also established the mean density of earth in 1796-97. He established it to be 5.448. He did this by carefully verifying Newton’s formula for gravitation using 2 metal balls and determining the attraction between them. This way he established the value of the gravitational constant and thus was the first to “weigh the earth”.

   Cavendish did not talk much. He did not even talk to his servants. It is said that he would write what he wanted to eat on a piece of paper and place it on the dining table. His servants would cook the dish and place it on the table and go away. Minimal contact with people. Maximum Science.

      Cavendish died in 1810 leaving behind a huge fortune and stacks of scientific manuscripts. In his memory the famous Cavendish laboratory in Cambridge was started.



|  Go, wondrous creature! mount where Science guides:                  

|  Go, measure earth, weigh air, and state the tides:                  

|  Instruct the planets in what orbs to run,                           

|  Correct old time and regulate the Sun;                              


Counter Irritant Effect


      The headache is inside the head(somewhere in the brain), and yet massaging the skull from outside  gives one relief. The place where you apply pressure (massage) is outside the skull and the pain is inside the skull. How can one feel relief? I asked my sister these questions and she gave me a very interesting medical reason for this.

      The effect is called counter irritant effect. To understand this we would have to understand how pain works. A large number of animals have brains and a large number do not. But all animals have a spinal cord.

The spinal cord is a primary quick action taking organ. If you touch a hot plate your hand immediately moves back. This happens in children too (where is brain is not very developed). THis decision of moving the hand back is taken by the spinal cord. And it is immediate. So we realize that the nerves that transmit feelings of pain first go to the spinal cord and then to the brain. If the spinal cord can act … it acts, otherwise it just ignores. If you have a headache the spinal cord cannot do anything so the pain goes to the brain and is “felt”.

        The pain inside the skin is not very well localized. You know that you have a headache in a particular area but you cannot know the “point” where the pain is. On the other hand the pain on the skin is very well localized. You know where EXACTLY it is. So evolution has given pain felt on the skin a higher priority over the pain in the internal organs. This is because a pain from outside may want you to run or fight. But the internal pain is something that cannot be immediately cured.

       So when there is a pain on the skin and pain inside the skin, the spinal cord will give preference to the skin pain and will not transmit the internal pain so much. So if you have an headache and you rub the head then the spinal cord keeps transmitting the pain/irritation on the skin to the brain and does not bother about the pain inside the skin (the headache).

      But as soon as the massage of the head stops the pain inside the skin comes back… so what to do? Apply a balm that constantly gives heat/cooling to the skin and constantly fools the spine to send only the heating/cooling signals to the brain.

      One more question> what if you have a stomach ache and you give the patient a head massage. That way the spine cannot be fooled. You have to apply the counter irritant to the same nerves that carry both the pains. So in a stomach ache you have to irritate the tummy skin to have relief.

      The acupressure and the acupuncture people know which set of nerves carry the same pain signals. So they put pressure on the skin from outside and the spine transmits only the outside pain giving relief from the internal pain.

      All ointments, balms etc use the counter irritant effect to give pain relief. Plus they also have some pain killer chemicals.

      Another thing that happens when you apply an irritant from outside is that the brain increases the blood supply to the area and the increased blood supply helps in internal pain too.