2 



RANDOM NOTES ON NATURAL HISTORY. 



of late years proved very injurious to the 

 elms throughout the Eastern States, and 

 shows clearl}' and plainly how it may be 

 satisfactorily dealt with. 



Destructive grasshoppers have been excep- 

 tionally- abundant during the summer. One 

 species (Ilelanoji/us destructor), peculiar to 

 the Pacific slope, has done much damage in 

 California, and special study has been given 

 to it on the spot. 



Remembering the fearful devastation 

 caused by the Rocky Mountain species be- 

 tween 1873 and 1877, the people of the 

 West have felt very keen anxiety as to the 

 future on account of the increased injury' 

 the present year. The entomologist has 

 given this subject very careful attention, 

 and, from the reports of special agents and 

 a full consideration of the subject, he con- 

 cludes that there is some danger of increase 

 in the next two or three years should the 

 weather prove favorable to the insect. 



But as an encouraging offset to this rather 

 gloomy prospect, he also considers that, un- 

 der conditions the most favorable to grass- 

 hopper increase, the injurj' can never be as 

 widespread as it has been in the past, owing 

 to the advance and increase in settlement. 



Other destructive insects have been vei'y 

 numerous, and a series of test experiments 

 have been made by agents stationed in New 

 Jersey, Indiana, and Iowa, with man}' in- 

 secticides which have been recommended 

 but never thoroughly tested. 



Another new field of investigation has 

 been added to the division by the appro- 

 priation by the last Congi-ess of $5,000 to be 

 devoted to the promotion of economic orni- 

 thology, or to the stud}^ of the interrelation 

 of birds and agriculture, an investigation of 

 the food, habits, and migration of birds in 

 relation to both insects and plants. 1 have 

 commissioned Dr. C. Hart Merriam, the 

 chairman of the committee on migration of 

 the Ornithologist's Union, to act with the 

 entomologist in this matter, and circulars 

 have been prepared and sent out, and the 

 work is now progressing in such a way as 

 to promise solid and vahiable results." 



In the work of the Ornithologists' Union 

 many of the readers of Random Notes are 

 personally interested, and all will look for- 

 ward to its results as presenting prime fac- 

 tors in the consideration of scientific agri- 

 culture. 



A Convenient Method for Finding the 

 Specific Gravity of Minerals. 



The principal thing needed to determine 

 the specific gravity of a mineral is an or- 

 dinary spiral spring; for quite large and 

 heavy specimens a window-curtain spring 

 will answer. The spring may be attached 

 b}' a nail or wooden peg which has been 

 driven in an upright piece of board of con- 

 siderable length ; care being taken to have 

 the support long enough so that the mineral 

 in hanging will not touch the board. The 

 mineral is now fastened to the lower end of 

 the spring by means of a string, a mark a 

 having been previously made on the up- 

 right piece of board opposite to the lower 

 end of the unstretched spring, the mineral 

 is allowed to hang free and draw out the 

 spring to its utmost. Now, on the upright, 

 mark the position of the same portion of 

 the spring as was before used in determining 

 a, and call this second point b. 



The distance from a to b will represent 

 the weight of the object in air. 



Now raise a vessel of water under the 

 specimen so that it shall be wholly immersed 

 and mark again on the upright the position 

 of the lower end of the spring and mark 

 it c. 



The distance from 6 to c will represent 

 the loss of weight in water. 



Now we know that the specific gravity of 

 a solid is equal to its weight in air divided 

 by its loss of weight in water ; therefore, 

 the distance from a to b divided by the dis- 

 tance from 6 to c will give the specific grav- 

 ity of the mineral in question. 



Suppose, for example, we wish to find 

 the specific gravity of a piece of Hematite. 

 We first note the natural position of the 

 spring, then attaching the specimen we 

 note that the weight of the mineral has 

 stretched the spring so that it extends five 

 inches. Next, we bring up under the speci- 

 men ajar of water until the mineral is be- 

 neath the surface but not touching the sides 

 or the bottom, and find that the spring has 

 lost one inch of its length. Five, the weight 

 in air, divided by one, the loss of. weight in 

 water, gives five as the specific gravity' of 

 Hematite. 



If it is desired to operate with small frag- 

 ments a more delicate spring must be used. 



