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The history of engineering can be roughly divided into four overlapping phases, each marked by a revolution:

Pre-scientific revolution: The prehistory of modern engineering features ancient master builders and Renaissance engineers such as Leonardo da Vinci.

Industrial revolution: From the eighteenth through early nineteenth century, civil and mechanical engineers changed from practical artists to scientific professionals.

Second industrial revolution: In the century before World War II, chemical, electrical, and other science-based engineering branches developed electricity, telecommunications, cars, airplanes, and mass production.

Information revolution: As engineering science matured after the war, microelectronics, computers, and telecommunications jointly produced information technology.

Research Aids for the Nineteenth Century

This is the calendar FAQ. Its purpose is to give an overview of the Christian, Hebrew, Persian, and Islamic calendars in common use. It will provide a historical background for the Christian calendar, plus an overview of the French Revolutionary calendar, the Maya calendar, and the Chinese calendar.

The reader will, I hope, agree that the "almost-antiseptic" washing machines of today don't have nearly the charm nor the character, albeit hazardous character, of those our grandmothers used. Our presentation herein is focused on the elegant washing machines which were powered either with gasoline engines or electric motors and were in use from 1900-1935. In 1920 there were over 1300 companies producing washers, and it is feasible here to show only a sampling of the myriad designs and shapes produced. Selected for illustration, are about 5% of the machines in my "hobby museum" located in Eaton, Colorado. Indeed, there is a lot more to see.

Whether you are an academic, family historian, collector, teacher or parent - welcome! All the worthwhile information about early maps can be found here, or from here. The 135 'pages' of this carefully organised site offer comment and guidance, and many, many links - selected for relevance and quality.

Mathematics represents a high level of abstraction attained by the human mind. In India, mathematics has its roots in Vedic literature which is nearly 4000 years old. Between 1000 B.C. and 1000 A.D. various treatises on mathematics were authored by Indian mathematicians in which were set forth for the first time, the concept of zero, the techniques of algebra and algorithm, square root and cube root.

n the Third Annual Report of the Henry Draper Memorial, attention is called to the fact that the K line in the spectrum of Zeta Ursae Majoris occasionally appears double. The spectrum of this star has been photographed at the Harvard College Observatory on seventy nights and a careful study of the results has been made by Miss. A. C. Maury, a niece of Dr. Draper. The K line is clearly seen to be double in the photographs taken on March 29, 1887, on May 17, 1889 and on August 27 and 28, 1889. On many other dates the line appeared hazy, as if the components were slightly separated, while at other times the line appears to be well defined and single.

Last year saw two interesting events in the world of double stars, both of them connected with an astronomer's old friend in the Big Dipper. While the early history of double star astronomy had to be completely rewritten after an examination of 17th century Italian manuscripts, its future at the beginning of the next millennium was briefly unveiled by the amazing precision of a new astrometric instrument, which will soon eliminate the difference between spectroscopic and visual binaries.

This paper deals with the English rejection of the Gregorian calendar in 1583, seeking to set this episode in its cultural, political and intellectual context. It concentrates particularly upon the work of John Dee, whose treatise of advice to the queen on the calendar reform is almost the only one of his major writings which has not (as far as I am aware) been studied in any depth in published writings.

From around 3000 BC onwards, astronomy in its most primitive form had developed. The sun, moon and changing seasons would have already been well studied. Perhaps the chief difference in thinking at that time was that the earth was flat. People genuinely believed that if you went far enough you would fall off the edge.