92 Mr. Patten's Air Pump, Gasomtter, Sfc. 



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. 



The sulphate which I procured from the above has been 

 sold in this city by C. Marshall, Junr. Druggist. 



Art. XVII. — Mk. Patten's Air Pump, GazometeVj and 

 Balance Beam. 



Mzvport, R. I. Mv. 1st. 1824. 



To THE Editor, 

 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 a reply. How far it may be 

 possible for two persons, at no inconsiderable 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 1 shall not pretend to decide, but shall content myself 

 with believing with the majority, that such a coincidence 

 though possible is not at all probable. That the same prin- 

 ciple should at the same time be discovered by two per- 

 sons, is I acknowledge more probable ; but to substan- 

 tiate this, some higher evidence than mere assertion will 

 be required. Now the fact is, that instead of the plans 

 having been proposed by me some months since, as I said, 

 it should have been some years — how many I cannot exact- 

 ly say, but the instrument that was constructed to try the 

 principle, and to which I alluded, was made in the winter 

 of 1821, and was then at least shown to a number of my 

 acquaintance, among whom was my particular friend and 

 classmate Prof. Ruggies 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- 

 wbom was Prof. D'Wolfe. The succeeding winter was 

 sp®n^ in New-York and it was then again shown to ma- 



