perspective, help to create the illusion. The Practical Mechanic's Journal of 1867 noted improvements over the alethoscope that were made to later models of the megalethoscope;1. The two lenses [one in front of the other] which may be removed through the small door for the purpose of cleaning them, instead of one fixed lens; 2. the substitution of several diaphragms, opening on a hinge...so as to inclose [sic] large and medium sized photographic views and cartes de visite, for the single diaphragm used in the Alethoscope; 3. the method of fixing ordinary portraits and small photographic views. By these improvements the magnifying of the views is considerably increased; the relief is more developed, but without exaggeration; the defects of sphericity [of the lens] are reduced to a minimum; greater clearness is obtained; and by the inclosing of the views in a frame, the eye is prevented from wandering to the margin at the expense of the stereoscopic effect. Each view is so disposed that it may be seen by reflection or as a transparency, and by day or by artificial light. The instrument is first placed on a table in front of a window, and the photographie view is introduced through the aperture... if it be desired to view the object by reflected light, the two reflectors...are opened so as to throw light on the same, but if by transmitted light, the reflectors are closed, the door...opened, and the light at the middle of the aperture passes through the back of the photographic view. Its effects are more striking with artificial light; and a gas burner or petroleum lamp answers the purpose very well. The observer places himself before the eye-glass...of the apparatus...moves forward or draws back the lens, by means of the two lateral handles... to suit his sight; and according as the photographic view is required to be on the wide or narrow side, the instrument... is turned a quarter turn from right to left by means of the buttons...which carry upwards, or to the right, the notch.. intended to receive the photographs. In order to prevent the eyes from being strained by the excess of light at the time the transparent views are changed a rough glass is placed between the two lenses when there is no photograph between the eye and the lamp. Two flat bars...sliding in a groove on the internal frame of the door...are