762 



THE POPULAR SCIENCE MONTHLY, 



toward the East. In 1859 it had reached 

 within a hundred miles of Omaha. In 1861 

 it had entered Iowa, and in 1865 had crossed 

 the Mississippi into Illinois. Thus on it 

 moved eastward, generally at about fifty 

 miles a year, though latterly the movement 

 must have been more rapid. The sad thing 

 is, that every swarm that moves leaves a 

 permanent colony behind. 



Every device has been employed to de- 

 stroy them. Paris-green has been dusted 

 on the plants. This will kill all it touches. 

 But its application is expensive, and not 

 without danger. It was found necessary to 

 use an ingenious machine drawn by two 

 horses. This consisted of a large box sup- 

 ported by wheels. The box was open at 

 the top, over which was a revolving flapper, 

 or fan, that brushed the vines over the box, 

 at the same time striking them, thus caus- 

 ing the beetles to fall to the bottom of the 

 box, where was a pair of revolving rollers, 

 between which they were crushed. There 

 were other kinds of machines, but this was 

 the most effective. 



The Colorado beetle is about half an 

 inch long, roundish, and in form much like 

 a lady-bug. It has a series of ten stripes 

 on each wing-cover, being alternately brown 

 and yellow. It is a very beautiful insect ; 

 but, alas ! it is among the most formidable 

 of those diminutive enemies of the industry 

 of man, whose depredations, even in the 

 brief history of our nation, has cost us, in 

 money loss of crops, more by many times 

 than the sum-total of all our wars. Already, 

 in Maryland, the ravages of the new-comer 

 are filling the farmers with dismay. 



Prof. Morse on the North American 

 Uiiionid^e. — In his paper on this subject, at 

 the recent meeting of the American Asso- 

 ciation, Prof. Morse explained, on the theory 

 of natural selection, why the fresh-water 

 mussels are so much more abundant in this 

 country than in Europe, and why they are 

 so much more numerous west of the Alle- 

 ghanies than on their eastern slope. The 

 families of fresh-water mollusks are few in 

 number, and are intimately related with 

 those families in the sea that have proved 

 capable of surviving admixture with fresh 

 water, and that commonly occur between 

 high and low water mark. Many animals 



have adapted themselves to the changing 

 influences which are liable to occur between 

 high and low water mark, such as inunda- 

 tions, fresh water, and rain. Others have 

 adapted themselves to brackish water, and, 

 to those forms that have survived, the fresh- 

 water mollusks are closely related. In this 

 struggle for adaptation to new conditions, 

 great modification of form takes place, a 

 fact illustrated and confirmed by what has 

 been observed in the case of the mya or 

 common clam. This belongs between high 

 and low water, and, although never yet so 

 far changed as to live in fresh water, it has 

 passed through almost innumerable modifi- 

 cations of form before giving up the strug- 

 gle. Now, referring to the past geological 

 history of this continent, we find, from the 

 successive upheavals of the Laurentian hills 

 to the North, the Alleghanies on the East, 

 and the Sierras on the West, a gradual in- 

 closing of wide inland seas, lagoons, whose 

 drainage must have been toward the Mis- 

 sissippi Yalley. These, in their gradual 

 transition from briny to fresh water, would 

 furnish all the conditions favorable to a 

 transformation from marine to fresh water 

 species ; to be followed by an infinite num- 

 ber of fresh-water forms, according as the 

 subsequent conditions varied. 



tse of the Actual Cantery.— The " actual 

 cautery " is commonly defined to be a red- 

 hot iron used for burning or disorganizing 

 the parts to which it is applied. The appli- 

 cation of a red-hot iron directly to the living 

 tissues is justly regarded as an extremely 

 painful operation ; but, if the iron be heated 

 to a white heat, it is absolutely painless. The 

 difference between the two is analogous to 

 the difference between a bullet speeding at 

 its maximum velocity, which may produce 

 mortal injury without pain, and a nearly- 

 spent bullet, which slowly lacerates the tis- 

 sues and causes agony. Dr. J. S. Camden, 

 writing in the Medical Times and Gazette, 

 recites as follows his own experience with 

 cauteries at different degrees of heat: 

 " When actual cautery," says he, " is to be 

 used, the iron must be heated till it is really 

 of a white heat, and looks almost as white 

 as white paper. If then applied it destroys 

 the part instantaneously, giving no pain ; 

 but it must be removed quickly on the heat 



