Proceedings of the Polytechnic Association. 1031 



grow in great luxuriance in their sterile bed. This explains the 

 malarious character of the location. The deca_y.ing mass beneath sent 

 np its niephitic vapors through the loose sand. 



Dr. A^anderwejde said he had listened with pleasure to the paper 

 of Professor Darby, and was sorry that he was not present at the 

 commencement of his remarks. What he has said is sound doctrine. 

 But in regard to ozone he wished to add a few words. It was dis- 

 covered by Schonbein, and was said to be a particular condition of 

 oxygen. We have an illustmtion of this in chemistry, as in the 

 diamond, graphite, sul])liur, etc. When sulphur is melted a little over 

 600 degrees, it becomes tough, and when poured into cold water 

 it changes from yellow to red, and then can be pulled out like 

 wax. Schonbein says, why cannot gaseous matter become the same ; 

 and this supposition has been adhered to for a long time. 



Bunsen says it may be equal atoms of hydrogen and oxygen. And 

 he suggests that it is II O^' or II 01 Xow it seems to be a combina- 

 tion that will very easily give otf its oxygen, and then that oxygen 

 will, of course, have very active properties. The oxygen will be in 

 a gaseous condition, and easily set free ; the hydrogen will let go the 

 sur]>lus of oxygen and comlnne with another. The great difficulty is 

 to measure the amount of watery vaj:>or in the atmosphere. We 

 always have a very active oxygen vrhich acts by its peculiar allotropic 

 condition. The decoloration of the iodide of starch, the iodide of 

 potassium mixed with starch has l)een supposed to be a test for ozone. 

 It has been said that when we find the paper becomes blue by the 

 impression of the ozone, it is a proof that ozone is in the air. But 

 every sweet substance will do tlie same thing. There is much yet to 

 be found out in relation to this matter, and to what are the best 

 means of purifying the air we breathe. In tlie city of Philadelphia 

 the water f)r daily use is pumped u]> into the reservoirs by steam, 

 and during some seasons tlie water is nut good. As this water h«s. 

 to pass several factories which empty into the river, the least dis- 

 tui'bing cause will make it quite turbid. So in the winter season, as 

 soon as the water is covered with ice, it becomes xqyy unpalatable,, 

 for the reason that no air can get to tlie water to purify it, and it is. 

 pumped into the reservoirs in its impure condition. 



Dr. L. Ih'adley remarkcil that the subject of malarious diseases is- 

 an important one, and perha])S . l)otli the germ theory and the- 

 chemical theory may Ijc correct. During his long experience he had 

 met with many of the diseases that are ascribed to malaria. He-. 



