Henry Dircks FRSE FCS (26 August 1806– 17 September 1873) was an English engineer who is considered to have been the main designer of the projection technique known as Pepper's ghost in 1858.

Dircks also investigated attempts at the invention of a perpetual motion device, writing that those who sought to create such a thing were "half-learned" or "totally ignorant".

Around the mid-1820s he began lecturing about chemistry and electricity while writing literary articles in the local press and scientific papers in the Mechanics' Magazine and other journals.

He also wrote a short treatise entitled Popular Education, a series of Papers on the Nature, Objects, and Advantages of Mechanics' Institutions, first printed in Liverpool in 1840.

[1] In 1843, Dircks and Thomas Hoblyn wrote an overview of the smokeless argand furnace, which was created by Charles Wye Williams in an attempt to solve the issue of smoky air in London.

[6] A Biographical Memoir of Samuel Hartlib, Milton’s Familiar Friend, With Bibliographical Notices of Works Published By Him, and a Reprint of His Pamphlet Entitled, "An Invention of Engines of Motion."

"[19] In Naturalistic Poetry, Dircks writes a series of four essays studying psalms and hymns written in the seventeenth, eighteenth, and nineteenth centuries.

[20] Dircks developed a way of projecting an actor onto a stage using a hidden room, a sheet of glass, and a clever use of lighting, calling the technique "Dircksian Phantasmagoria".

[20] Popular science lecturer John Henry Pepper saw the concept and replicated it on a larger scale, taking out a joint patent with Dircks.

[21] 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 even after Dircks signed over all financial rights.

To Mr. Dircks belongs the honour of having invented him, or as the disciplines of Hegel would express it, evolved him from out of the depths of his own consciousness; and Professor Pepper has the merit of having improved him considerably, fitting him for the intercourse of mundane society, and even educating him for the stage.

"[26] His book Perpetuum mobile; or, Search for self-motive power, published in 1861, examined many attempts at creating such a device, and has since been cited by other science writers on the subject.

Dircks summarised the ongoing efforts of inventors:A more self-willed, self-satisfied, or self-deluded class of the community, making at the same time pretension to superior knowledge, it would be impossible to imagine.

[11] Dircks study of perpetuum mobile built upon the earlier exploration of the subject by Simon Stevin, who wrote: “It is not true [falsum] that the globe moves by itself with an endless movement [aeternum]”.