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different kinds of saltpeter, some kinds requiring nearly double the 

 amount that would be required of others. 



On the 27th of August I sprinkled a cluster of horse-radish leaves, 

 which were badly infested with cabbage worms, with a solution com- . 

 posed of one tablespoonful of saltpeter, an equal quantity of salt 

 dissolved in a cupful of hot water, and diluted with about two quarts 

 of water. The solution was sprinkled on the leaves at about half 

 past nine o'clock in the forenoon, when the sun was shining brightly. 

 At the time of applying the solution there were about a dozen worms 

 of various sizes on the leaves ; two days later only two of the worms 

 remained. On some of the leaves were a few quite large spots that 

 had been killed by the solution, but the leaves were not injured to 

 any great extent by it. 



On the 12th of the following September I sprinkled another cluster 

 of horse-radish leaves, which were badly infested with these worms, 

 with a solution composed of about one-fourth of a tablespoonful of 

 the same kind of saltpeter as that used above, and an equal quan- 

 tity of salt, dissolved in hot water and diluted with about one quart 

 of cold water. This was applied at about half past eleven o'clock 

 in the forenoon, while the sun was shining brightly. It apparently 

 had but little effect upon the worms, except on a few of the 

 younger ones. 



From this it would appear that in order to be "perfectly effectual, 

 it would be necessary to make the solution so strong that it would 

 injure the plants upon which it was sprinkled, unless it be that the 

 plants are hardier than the horse radish ; and this, like most other 

 remedies, will be more fatal to the young worms than it will be to 

 those more advanced. 



Several writers recommend the use of hot water for destroying 

 these worms ; but the following experiments which I made with it 

 last year do not prove it to be very desirable. 



On the 14tli of May I made a number of experiments, with a view 

 of ascertaining the number of degrees to which water could be heated 

 and be applied to plants without injuring them. The day on which 

 these experiments were made was cloudy, the sun shone occasion- 

 ally, and the thermometer placed where both the sun and wind 

 could strike it, indicated a temperature of 68° Fahrenheit. The 

 plants experimented upon were dandelion, horse-radish and tame 

 cherry, and the water was applied to the same plant only once. 



At 130° the water did not affect any of the plants. At 140° dan- 

 delion was slightly affected, but horse-radish and cherry were not 

 perceptibly injured. At 150° dandelion was killed, and horse-radish 

 and cherry slightly injured. At 160° horse-radish was killed, and 

 cherry was killed in spots. At 170° all of the plants were killed, the 

 leaves withering sooner than at 160°. 



It will be thus seen that water cannot be heated above 140° and be 

 applied to plants like the dandelion without injuring them, while 

 on plants as hardy as the tame -cherry the water may be heated to 

 150° and be applied to them without injuring them, but it is not 

 likely that they would stand a greater degree of heat than this. 



On the 2d of the following June I made a number of experimenis 

 for the purpose of ascertaining the number of degrees below 140° 

 that water could be heated and be applied to caterpillars and destroy 

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