John Henry "Professor" Pepper (17 June 1821 – 25 March 1900) was a British scientist and inventor who toured the English-speaking world with his scientific demonstrations.

He is primarily remembered for developing the projection technique known as Pepper's ghost, building a large-scale version of the concept by Henry Dircks, which Pepper first publicly demonstrated during an 1862 Christmas Eve theatrical production of the Charles Dickens novella, The Haunted Man and the Ghost's Bargain, causing a sensation among those in attendance at the Regent Street theatre in London.

[1][2] Pepper also oversaw the introduction of evening lectures at the Royal Polytechnic Institution (University of Westminster) and wrote several important science education books, one of which is regarded as a significant step towards the understanding of continental drift.

[3] He introduced a series of evening classes covering educational and trade topics, and lectured by invitation at some of the most prestigious schools across England, including Eton, Harrow, and Haileybury.

Liverpudlian engineer Henry Dircks is believed to have devised a method of projecting an actor onto a stage using a sheet of glass and a clever use of lighting, calling the technique "Dircksian Phantasmagoria".

[7] Some reports have suggested that, at the time, Pepper claimed to have developed the technique after reading the 1831 book Recreative Memoirs by famed showman Étienne-Gaspard Robert.

People returned to the theatre repeatedly in an attempt to work out the method being used; famed physicist Michael Faraday eventually gave up and requested an explanation.

[4] 1861's The Playbook of Metals, built upon the work of Antonio Snider-Pellegrini and is regarded as an important step in the understanding of continental drift.

In 1863 he illuminated Trafalgar Square and St. Paul's Cathedral to celebrate the marriage of Edward Albert, Prince of Wales, and Alexandra of Denmark.

On 21 December 1867 at a banquet of "noblemen and scientific gentlemen" Pepper arranged for a telegram to be sent between Arthur Wellesley, 2nd Duke of Wellington and Andrew Johnson, President of the United States who was in Washington at the time.

He took out a front page advertisement in the 30 January 1882 issue of The Brisbane Courier to publicise the event, scheduled for 4 February 1882 at the Eagle Farm Racecourse.

He gathered a range of materials including ten swivel guns, powerful rockets from HMS Cormorant, a land mine, and a large quantity of gunpowder.

The plan would be to create a bonfire that would billow smoke into the air, then an explosion in the clouds would contribute to a change in their electrical condition.

[13] Pepper felt very badly treated by fellow scientists and the general public and in a letter written to The Brisbane Courier dated 27 May 1882 he stated: "My experiment in Queensland was received with such derision and insults that in the face of those hard steely railings I shall leave to others the honour and expense of trying to do good by gently persuading the clouds to drop fatness.

In another letter to The Brisbane Courier in April 1884, Pepper referred to one of them, saying that he hoped the scientist would "not be unappreciated or treated with the ribald and narrowminded jokes and judgments that were showered on my head.