PROCEEDINGS. 121 



objects in the outer world ; also working models demonstrating 

 the value of the spinal curves in diminishing the evil effects of 

 mechanical violence. 



The Rev. Robert Harley, m.a. (Oxon.J, f.r.s., exhibited Charles 

 third Earl Stanhope's Arithmetical machine bearing date 1780, 

 also his ' Demonstrator ' an instrument for the performance of 

 logical operations which he described as follows : — 



" On the Stanhope Logical and Arithmetical Machines." 



Abstract. 



Charles third Earl Stanhope* is known to science by his 

 mechanical inventions. The works to which he owes his celebrity 

 are chiefly the following : — -A printing press and a microscopic lens, 

 both of which bear his name, a method of securing buildings from 

 fire, an arithmetical machine, a monochord for tuning musical 

 instruments, certain improvements in the process of stereotype 

 printing and in the construction of locks for canals, and a steam- 

 boat, or, as it was described by its inventor, a vessel to sail " with- 

 out the aid of either wind or tide or oars." But until within 

 recent years it does not seem to have been generally known that the 

 Earl devoted a large portion of his life to the study of logic and 

 that he invented an instrument for the mechanical performance 

 of logical operations. None of the accounts which appeared of 

 his intellectual labours contained any allusion to his researches 

 on the subject, or to the curious contrivance which he called 



The Demonstrator. 



His logical speculations which employed his thoughts more or less 

 during a period of thirty years, remained absolutely unpublished 

 and unnoticed down to the time when the present Earl found 

 among the relics of his scientific ancestor the logical instrument 

 which I have now the honour to exhibit to the Society. At the 

 suggestion of the late Mr. William Spottiswoode, then President 

 of the Royal Society, this instrument was placed in my hands for 

 examination, and I soon discovered that it was constructed with 

 a view to the mechanical solution of logical problems. The dis- 

 covery led to a search being made in the archives of the Stanhope 

 family for letters and other manuscripts relating to the Earl's 

 logical inquiries. Such remains as could be found were entrusted 

 to me for a time, and I studied them with care, embodying some 

 of the results of my studies in a paper entitled " The Stanhope 

 Demonstrator : an instrument for performing logical operations," 

 which was communicated to the British Association at the 

 meeting in Dublin, 1878. This paper with some additions 



* Born 3rd of August, 1753, died 15th December, 1816. 



