CHEMICO-AGRICULTURAL TOUR. 143 



The same gentleman who conducted me all through the series of 

 laboratories and chemical apartments of the university, kindly 

 showed me some very striking experiments with the prism, illus- 

 trative of its use in chemical analysis. The apparatus he exhibited 

 was simply a wedge-shaped vessel of glass, which, being filled 

 with a vcr}" dilute solution of sulphate of indigo, was placed in 

 front of the flame of a jet of coal-gas, and then a platinum wire, 

 being dipped in different metallic solutions, was placed in the flame 

 and afterwards viewed through the prism, when different phenom- 

 ena were observed, which were in some cases highly characteristic 

 and thus afforded a very delicate and ready means of detecting the 

 presence of different metals and their salts. 



I was so much pleased with the experiments which I saw with 

 this simple instrument, that on my return I got one constructed for 

 the use of the laboratory of this Societ}^, and have no doubt it will 

 prove of much use in different analytical operations carried on 

 there. Finally, I obtained much information as to various methods 

 of analytical determination, &c., employed in that celebrated chem- 

 ical laboratory, which has been so intimately connected, not only 

 with the advancement of chemical science, but likewise with that 

 of agriculture during the last quarter of a century. 



In going from Frankfort to Giesse'n, I passed by the salt-works 

 at Nauheim, and saw from the railway-carriage the arrangements 

 adopted for concentrating the brine at those works, where, I un- 

 derstand, there exists a remarkable natural brine-fountain, which 

 issues at certain intei'vals with great velocity from an opening in 

 the ground, and is propelled upwards to a considerable height. 

 This arrangement, as well as I could see from the railway, consist- 

 ed in letting the brine trickle down from a considerable height 

 through a quantity of furze bushes placed on a large kind of frame- 

 work, to the top of which it was conveyed. In this manner a very 

 extended surface of the salt liquid was exposed to the air, by which 

 its evaporation was greatly accelerated. 



From Frankfort I proceeded by the Tannus railway to Wiesba- 

 den, the capital of the Duchy of Nassau, which is situated in a 

 beautiful valley, surrounded by picturesque hills, and is celebrated 

 for its mineral baths and hot springs. Arriving at this very fash- 

 ionable German watering place, I visited the agricultural school or 

 college at Geisberg, which is the chief agricultural seminary of 

 Nassau, and is beautifully situated on a hill, a short distance from 



