IIALLAM'S HISTORY OF LITERATURE. Ill 



Cavendish experiment, and even took some part in the 1841. 

 Keport on the Commission for restoring the National 

 Standards, to which he had devoted so much time and 

 thought. This Commission was appointed in 1838. The 

 Report was sent in in 1841. On the appointment of a 

 new Commission in 1843 to reconstruct the Standard 

 Scales, Mr. Baily recovered sufficiently to undertake the 

 Standard of Length, but did not live to complete it. 



Mr. Hallam's History of the Literature of the Middle 

 Ages was at this time coming out, and after the publica- 

 tion of the first edition Mr. De Morgan sent the author 

 some observations on the history of the Mathematicians 

 of the period embraced in the first volume. What his 

 criticisms were can only be guessed by Mr. Hallam's reply, 

 as I have not his own letter. 



Dec. 12, 1841. 



I am much obliged by your correction of some inaccuracies 

 in the first volume of my History of Literature, which will be 

 of use to me in the new edition which I am now preparing. I 

 am always thankful for such communications, which are at least 

 a sign that the book is thought worthy of them. 



In reply to further criticism, further correspondence 

 took place two years later, Mr. Hallam's letter touching 

 on the subject of Logic, which had assumed so definite 

 and important a form in Mr. De Morgan's thoughts, 

 and which was afterwards treated in connection with 

 points of original discovery in his Formal Logic. 



I shall pay all attention to them (your remarks) in any new H. Hallam. 

 edition, and will look again at some of the works in which your 

 more expert eye lias detected rny errors. I certainly searched 

 in vain for the triangle of forces so called in Stevinus, and I was 

 a little more led to doubt of his using it, as Montucla says, be- 

 cause the only demonstration with which I am acquainted 

 involves the third law of motion ; but that, according to the 

 general opinion, was not laid down till long afterwards. Perhaps 

 Stevinus might assume it on metaphysical principles without 

 experiment. 



