146 Miscellaneous Observations on Insects. 



one of them is seen in the figure. A disk of thin, varnished card, 

 four inches in diameter, being placed underneath, and, by means 

 of three small pins thrust through it near the edge, separated 

 from the plate as far as possible without ceasing to be sustained, 

 namely, four tenths of an inch, on blowing strongly through 

 the tube, the colored water rose in the branch a of the glass 

 tube four inches above its level in the branch h, showing the 

 air in the tube T at the place of junction of the leaden tube, 

 four inches and a half above the tin plate, to be rarer by about a 

 hundredth part, than the surrounding atmosphere. In a similar 

 manner, the air in any part of the tube nearer the plate, is found to 

 be rarer, and, in any part farther from it, to be denser than the 

 surrounding atmosphere. These results can be explained only by 

 referring them to a kind of retrograde influence of the primary 

 rarefaction. The current in the lower part of the tube, meeting 

 with diminished resistance, in consequence of the attenuated state 

 of the air between the disks, rushes forward with greater velocity 

 than that with which it issues from the mouth ; and this accele- 

 ration of velocity, producing a secondary rarefaction, extends the 

 limits of the primary inwards, as just shown, and outwards by 

 increasing the momentum of the radiating currents. 



Boston, December 16, 1840. 



Art. XVII. — Miscellaneous Observations on Insects, S^x.] by Dr. 

 John T. Plummer, of Richmond, Indiana, in letters to the Ed- 

 itors, dated Aug. 11, and Dec. 12, 1840. 



Without the advantage of systematical works, in a desultory 

 way, I have long been a deeply interested observer of the habits 

 and various developments of living insects, and have witnessed 

 many curious phenomena pertaining to them. My botanical re- 

 searches, prosecuted over hill and dale, through wet and dry, for 

 the last fourteen years, have often brought me into contact with 

 those diminutive specimens of creation, the insect tribes, and have 

 thus, no doubt, presented some things to my view, which other- 

 wise I should not have seen. Last summer I picked a dozen re- 

 cently fallen plums from beneath one of my trees, and placed 

 them in a glass jar, one half filled with earth, for the purpose of 



