116 Want of Identity between Microlite and Pyrochlore. 



observations at some distance from this line would lead us to look 

 for it about three quarters of a degree farther west than the posi- 

 tion here assigned. 



P. S. Seventeen hundred Errata in Hutto?Vs Table of Products. 



In solving equations of condition by the method of minimum 

 squares, I have been accustomed to form the products by the aid of 

 Button's Table. I entertained no doubt of its accuracy, until, on 

 verifying one of my operations, I discovered in the Table an error 

 which I presently perceived to run through almost an entire folio 

 page. The case occurs on page 20, the product of 361 by 15 being 

 given 5315 instead of 5415, and as the products appear to have 

 been derived from each other by addition, this error is propagated 

 to the bottom of the page, affecting thus 1700 products. 



Art. X. — On the Want of Identity between Microlite and Pyro- 

 chlore ; by Charles Upham Shepard, M. D., Prof. Chem. in 

 the Medical College of the State of South Carolina. 



Prof. Silliman having apprised me on my recent arrival in 

 town, that a paper was about to appear in this Journal by Messrs. 

 Teschemacher and Hayes of Boston, the object of which would 

 be to establish the identity of Microlite with Pyrochlore, and being 

 permitted by the editors, I hasten to reply in the same number. 



The opitiion of the identity originated with Mr. Teschema- 

 cher; and is expressed without the slightest reserve, resulting 

 as he remarks, " from a close examination of several crystals of 

 the mineral named Microlite;" but Mr. T. singularly enough 

 omits altogether, the results of any researches bearing on the 

 point to be established, if we except the mention of a minera- 

 logical property which is simply descriptive, never character- 

 istic, viz. the circumstance that in Microlite, the color is " trans- 

 parent (!) straw-yellow to brick-red and dark brown !"* For the 

 full confirmation of his opinion, he then refers to the analysis of 

 Mr. Ha¥es, which was undertaken at the request of the Chem- 

 ical Society of Boston. 



* In this account of color however, ray specimens do not agree. 



