Sir John Frederick William Herschel, 1st Baronet KH FRS (/ˈhɜːrʃəl, ˈhɛər-/;[2] 7 March 1792 – 11 May 1871)[1] was an English polymath active as a mathematician, astronomer, chemist, inventor and experimental photographer who invented the blueprint[3][4][5] and did botanical work.

[10][11] Herschel's A preliminary discourse on the study of natural philosophy, published early in 1831 as part of Dionysius Lardner's Cabinet cyclopædia, set out methods of scientific investigation with an orderly relationship between observation and theorising.

This became an authoritative statement with wide influence on science, particularly at the University of Cambridge where it inspired the student Charles Darwin with "a burning zeal" to contribute to this work.

Herschel collaborated with Thomas Maclear, the Astronomer Royal at the Cape of Good Hope and the members of the two families became close friends.

Herschel combined his talents with those of his wife, Margaret, and between 1834 and 1838 they produced 131 botanical illustrations of fine quality, showing the Cape flora.

Even though their portfolio had been intended as a personal record, and despite the lack of floral dissections in the paintings, their accurate rendition makes them more valuable than many contemporary collections.

Intrigued by the ideas of gradual formation of landscapes set out in Charles Lyell's Principles of Geology, he wrote to Lyell on 20 February 1836 praising the book as a work that would bring "a complete revolution in [its] subject, by altering entirely the point of view in which it must thenceforward be contemplated" and opening a way for bold speculation on "that mystery of mysteries, the replacement of extinct species by others."

Herschel himself thought catastrophic extinction and renewal "an inadequate conception of the Creator" and by analogy with other intermediate causes, "the origination of fresh species, could it ever come under our cognizance, would be found to be a natural in contradistinction to a miraculous process".

Taking a gradualist view of development and referring to evolutionary descent from a proto-language, Herschel commented: Words are to the Anthropologist what rolled pebbles are to the Geologist – battered relics of past ages often containing within them indelible records capable of intelligent interpretation – and when we see what amount of change 2000 years has been able to produce in the languages of Greece & Italy or 1000 in those of Germany France & Spain we naturally begin to ask how long a period must have lapsed since the Chinese, the Hebrew, the Delaware & the Malesass [Malagasy] had a point in common with the German & Italian & each other – Time!

[22][23] The document was circulated, and Charles Babbage incorporated extracts in his ninth and unofficial Bridgewater Treatise, which postulated laws set up by a divine programmer.

[20] When HMS Beagle called at Cape Town, Captain Robert FitzRoy and the young naturalist Charles Darwin visited Herschel on 3 June 1836.

[24] Herschel returned to England in 1838, was created a baronet, of Slough in the County of Buckingham,[6] and published Results of Astronomical Observations made at the Cape of Good Hope in 1847.

In this publication he proposed the names still used today for the seven then-known satellites of Saturn: Mimas, Enceladus, Tethys, Dione, Rhea, Titan, and Iapetus.

Herschel made experiments using photosensitive emulsions of vegetable juices, called phytotypes, also known as anthotypes, and published his discoveries in the Philosophical Transactions of the Royal Society of London in 1842.

[6] Herschel discovered sodium thiosulfate to be a solvent of silver halides in 1819,[33] and informed Talbot and Daguerre of his discovery that this "hyposulphite of soda" ("hypo") could be used as a photographic fixer, to "fix" pictures and make them permanent, after experimentally applying it thus in early 1839.

Herschel wrote many papers and articles, including entries on meteorology, physical geography and the telescope for the eighth edition of the Encyclopædia Britannica.

[34] Herschel invented the actinometer in 1825 to measure the direct heating power of the Sun's rays,[35] and his work with the instrument is of great importance in the early history of photochemistry.