208 Memoir of Rev. John Prince, LL. D. 



brother who worked with him, was very sick of a fever, and requir- 

 ed all his attention. The brother died. In two days more he took 

 the fever himself, and died in ten days, and left me destitute of 

 workmen to finish the matters I had undertaken. I got the instru- 

 ment from his shop as soon as I could in the unfinished state, and 

 went to work myself to complete it ; and when I had done it to my 

 own satisfaction, as I supposed, to my great disappointment and 

 mortification, I found all the labor was lost. For, on putting the 

 needle into the box, which is of a parallelogram form, about six 

 tenths of an inch in width, I found the box, though made of brass, 

 attracted the needle to its side and would not allow it to play freely. 

 This was a circumstance entirely new and unexpected. I never 

 had an idea of any kind of brass being magnetic, and could not ac- 

 count for the phenomenon for some time. But on trying several 

 other pieces I found that the box was not the only one that attracted 

 the needle. Several pieces did the same; others did not. This 

 quality must be owing to the impurity of the brass. Some steel 

 filings or small particles of iron must have accidentally mixed with 

 it in casting. It would have been fortunate for me if I had made 

 the discovery before it was worked ; but the thought never occurred 

 to me. Too much of our knowledge (considering the shortness of 

 life) comes to us by dear bought experience." 



The foregoing extract may serve to give some idea of the great 

 inconveniences to which Dr. Prince was put, as a philosophical me- 

 chanician, from the want of workmen, and from the necessity of 

 accumulating for himself his own " dear bought experience," with- 

 out obtaining any benefit from the experience of others. 



In looking through these manuscript volumes, we perceive, from 

 the beginning to the end, the evidences of his wisdom, ingenuity, 

 and skill. In one of his letters (Sept. 24, 1795,) he recommends a 

 new construction of thermometers, in which zero should be at the 

 freezing point of mercury, thereby avoiding the inconvenience of 

 having both plus and minus in the scale. 



In another letter (Dec. 4, 1795,) he describes some improvements 

 he had introduced in the construction of an equatorial. 



Feb. 13, 1797, he gives an account of a magic lantern, contri- 

 ved and constructed by him on a new and extensive scale. 



He thus introduces the description of another of his inventions, 

 in a letter to William and Samuel Jones, of London, Oct. 20^ 

 1797 — " I have lately constructed a very large microscope for my- 



