210 REPORT OF NATIONAL MUSEUM, 1904. 



A paper by Robert McCauslin, read before the American Philosoph- 

 ical Societ}^ of Philadelphia in 1789 and published in 1793, conveys a 

 good idea of the crude condition of analytical chem- 



C i unlit ion of . liiii li 



Analytical istry at that date and enables one to well appreciate 



Chemistry in 1789. ■-,.„.■■. . • i 



the difficulties under which the mineralogists labored. 

 In describing a " mineral substance'' 1 found near the falls of Niagara, 

 he wrote: 



In order to determine the nature of this substance, I made the following experi- 

 ments: 



Exp. 1st. I put an opaque piece, weighting fourteen grains, into the vitriolic acid 

 diluted with three times its quantity of water, and let it remain there twenty-four 

 hours, shaking it now anil then. Not the least effervescence ensued, and on taking 

 out the piece it weighed near one grain more than when it'Vas put in, although care 

 was taken to absorb the moisture which was upon its surface. This experiment was 

 repeated with a shining piece, and with exactly the same result. 



Exp. 2nd. When put into vinegar it did not produce the least effervescence. The 

 vinegar having stood upon it for sometime, it was then poured off and spirit of 

 vitriol dropped into it, yet not the least precipitation ensued. 



That I might not be led into error by the vinegar not being good of its kind, I 

 repeated these experiments with chalk; and as both effervescence and precipitation 

 took place it was evident there was no defect in the vinegar. 



Exp. 3rd. A small piece was exposed to the heat of a blacksmith's forge during 

 fifteen hours. Upon taking it out and pouring water upon it no ebullition ensued; 

 nevertheless it tasted like weak limewater; being then divided into two portions, a 

 solution of mild fixed alkali was dropped into the first, and immediately a precipita- 

 tion ensued. The second portion being exposed to the air in a tea cup soon, con- 

 tracted a changeable film, which next morning was become very thick, resembling 

 in every respect that of limewater. 



Exp. 4th. Hot water being poured on some of this substance reduced to powder 

 and the whole suffered to settle, the clear liquor had not the taste of limewater as 

 in the 3rd experiment; nevertheless a solution of mild fixed alkali being dropped 

 into it as copious a precipitation ensued as when the earth had undergone calcina- 

 tion. 



As I had neither the nitrous nor muriatic acids, nor even caustic fixed alkali, I 

 had it not in my power to make any trials with them. 



From these experiments we may perhaps be authorized to draw the following 

 conclusions: 



1st. That this concrete is not an alkaline earth, as it is not affected either by the 

 vitriolic or the vegetable acids. 



2ndly. We may with more probability say that it is a combination of an acid with 

 a calcareous earth, and that it might with propriety be ranked amongst the selenites. 

 This supposition is founded on the following reasons: First, it appears from the 

 fourth experiment that it is practically soluble in water, and that its earth can be 

 precipitated by a mild fixed alkali; secondly, the third experiment shews evidently 

 that its earth is of the calcareous kind, as appears by the styptic taste and changeable- 

 colored film, agreeing exactly with common limewater. It seems probable that the 

 vehemence of the fire had in part expelled the acid, leaving a portion of the mass in 

 the state of quicklime. 



Of more direct geological bearing is a letter from Benjamin De Witt 

 to the Philadelphia Academy, printed in the second volume (IT'.'M) 



