During the 19th Century (and to a certain extent; the 18th century) people of English descent (I'm not saying all English people thought this but racism was more prevalent and widely accepted during this time) believed that their race was superior to everyone else. I would like to know what caused this belief.
Basically it came down to an idea of scientific racism. With the advent of the age of enlightenment came this idea that all matters of things could be determined by science and the scientific method. The idea came about that all things must be able to be explained by science. What people saw in their lives was that the West had the most technology and were the most powerful countries on earth thus the greatest race.
Once people had that idea in their heads they went looking for evidence. The major influence on this scientific racism was the work of a man called Samuel Morton who wrote a book called Crania Americana, An Inquiry into the Distinctive Characteristics of the Aboriginal Race of America and Crania Aegyptiaca In this he measured the skulls of all the various races around the world and "discovered" that the English and Germans had the largest brains and the Aboriginal people of Australia had the least. Now obviously his scientific method was hugely flawed in that he made no allowance for male and female skulls not even taking into account that brain size has no bearing on intelligence. Now once this work was published in there is a large section of a very good book The mismeasure of Man which goes into this in much greater detail. In Morton's book he discusses the various races and comes to the following conclusions.
Whites "The Caucasian Race is characterized by a naturally fair skin, susceptible of every tint; hair fine, long and curling, and of various colors. The skull is large and oval, and its anterior portion full and elevated. The face is small in proportion to the head, of an oval form, with well-proportioned features. ... This race is distinguished for the facility with which it attains the highest intellectual endowments. ... The spontaneous fertility of [the Caucasus] has rendered it the hive of many nations, which extending their migrations in every direction, have peopled the finest portions of the earth, and given birth to its fairest inhabitants."
Asians "This great division of the human species is characterized by a sallow or olive colored skin, which appears to be drawn tight over the bones of the face; long black straight hair, and thin beard. The nose is broad, and short; the eyes are small, black, and obliquely placed, and the eyebrows are arched and linear; the lips are turned, the cheek bones broad and flat. ... In their intellectual character the Mongolians are ingenious, imitative, and highly susceptible of cultivation [i.e. learning]. ... So versatile are their feelings and actions, that they have been compared to the monkey race, whose attention is perpetually changing from one object to another.
Africans "Characterized by a black complexion, and black, woolly hair; the eyes are large and prominent, the nose broad and flat, the lips thick, and the mouth wide; the head is long and narrow, the forehead low, the cheekbones prominent, the jaws protruding, and the chin small. In disposition the Negro is joyous, flexible, and indolent; while the many nations which compose this race present a singular diversity of intellectual character, of which the far extreme is the lowest grade of humanity. ... The moral and intellectual character of the Africans is widely different in different nations. The Negroes are proverbially fond of their amusements, in which they engage with great exuberance of spirit; and a day of toil is with them no bar to a night of revelry. Like most other barbarous nations their institutions are not infrequently characterized by superstition and cruelty. They appear to be fond of warlike enterprises, and are not deficient in personal courage; but, once overcome, they yield to their destiny, and accommodate themselves with amazing facility to every change of circumstance. The Negroes have little invention, but strong powers of imitation, so that they readily acquire mechanic arts. They have a great talent for music, and all their external senses are remarkably acute."
In reading this you can see what they thought and why they did. People of the time thought of themselves as logical who had evidence for what they thought.
Crania Americana
The Mismeasure of Man
http://robinlea.com/pub/The_mismeasure_of_man.pdf from pg 82