92 Mr. Patien’s Air Pump, Gazometer, &c. 
the crude substance as Quinine does to Peruvian Bark. It 
‘is well worthy the attention of Physicians, as the quality of 
rhubard is so various that the dose is very uncertain. This 
preparation will be of uniform strength, and may be admin- 
istered safely to new born infants. 
he sulphate which I procured from the above has been 
sold in this city by C. Marshall, Junr. Druggist. 
Art. XVII.—Mnr. Parren’s Air Pump, Gazometer, and 
Balance Beam. 
Newport, R. L Nov. ist. 1824, 
To rue Epvrror, 
Dear Sir, 
The remarks of Prof. Dana upon the Air Pump that 
you did me the honor to insert in your Journal, ne- 
cessarily require from me areply. How far it may be 
possible for two persons, at no inconsi distance 
apart, and without a knowledge of each others plans to con= 
struct two instruments so similar in their “ details,” that it 
shall be difficult to tell the one from the other, is a ques- 
tion { shall not pretend to decide, but shall content myself 
with believing with the majority, that such a coincidence 
though possible is not at all prebable. That the same prin- 
ciple should at the same time be discovered by two per- 
sons, is I acknowledge more probable; but to su 
acquaintance, among whom was my particular friend and 
classmate Prof. Ruggles of the Columbian College at 
Washington, and Mr. James Stevens a remarkably intelli- 
gent and ingenious civil engineer of this place; it was also 
known to several scientific gentlemen in Providence, one of 
whom was Prof. D’Wolfe. The succeeding winter was 
spent in New-York and it was then again shown to ma- 
