[ no place ]: Self published 1845. Oblong 12 x 9 1/4 inches. Tan paper, printed in black lettering. Folded vertically, with several early tape repairs on the verso. Paper tanned. Good. 
Dr. William Mather notes in this "traveling lecture" broadside that he will be showing experiments on Magnetism and the newly discovered power of Electro-Magnetism by use of an Electro-magnetic Engine moving upon a Circular Railway. Further, the broadside notes that there is the possibility of examing "Some portion of the apparatus" with explanations given after the Lecture. Traveling lectures of this sort we haven't seen before - class lectures on a paid basis in schools yes, but this form no. Perhaps the hope ("Admittance to the first Lecture, gratuitous, and a general attendance is invited") was to create a ready audience of paying attendees over time.
The presenter was most likely Dr. William Mather, a popular lecturer, and one of the founders of Fairfield Academy. "Dr. William Mather (1802-1890), a descendent of Cotton Mather, was a son of Captain Moses Mather, an early settler of Herkimer County and one of the founders of Fairfield Academy. In 1826, Mather graduated from Fairfield Medical College with the degree of M.D. As he had from boyhood been "an ardent lover of the science of chemistry," he turned his attention to that subject and from 1828 to 1868 was one of the most popular lecturers in this country. He married Mary Ann Buell in 1836, and the two had three children. In 1838 he was appointed instructor in chemistry at the Hamilton (New York) Literary and Theological Seminary and in 1841 was elected professor of chemistry at the Castleton (Vermont) Medical College. From 1852 to 1868 he was professor of chemistry, mineralogy, and geology at Madison (now Colgate) University in Hamilton. He was also the president of Fairfield Seminary for more than a quarter of a century." (Syracuse University finding aid for the Mather Collection)
No copies in OCLC/Worldcat. Rare Book Hub shows only this example offered in 2004 by M&S Books, Catalog 77.