August 20, 1886.] 



SCIEJSrCE. 



165 



others. Will we not, therefore, have to cut down 

 very materially the great length of time generally 

 believed to have elapsed in this region from the 

 beginning of this lacustrine period to the present 

 time, when we find that a great portion of the sedi- 

 ment that once filled the lakes is due, not to the pro- 

 ducts of erosion, as has hitherto been supposed, but 

 to repeated showers of volcanic dust ? Again, do not 

 these volcanic materials, which must have fallen in 

 showers over a large extent of country, — accumulat- 

 ing in some cases in beds forty to ninety feet thick, 

 — account for the perfect preservation of the verte- 

 brate remains which characterize the formations in 

 so many parts of the west ; and is there not also 

 suggested one possible cause for the extinction of 

 some of the many groups of animals which have at 

 present no descendants in this region, and whose only 

 remains are the bony fragments found in these lacus- 

 trine deposits ? J 



•^ A. C. Peale. 



U. S. geological survey. , 



Carnivorous prairie dogs. — Carnivorous orioles. 



The statement of E. W. Shufeldt that his pair of 

 young prairie dogs took kindly to a meat diet {Sci- 

 ence, viii. p. 102) attracted my attention and inter- 

 est, for it recalled to my mind an experience of my 

 own in the summer of 1838. Having a pair of the 

 marmots at this moment under observation here, I 

 determined to try them with a piece of raw beef, 

 and the eagerness with which they plunged at it (for 

 their avidity cannot be characterized by any milder 

 word) was certainly something very astonishing. 

 Their ordinary vegetable food they take quietly, but 

 the beef seemed to set them frantic. They acted as 

 though they were famishing, — they seized it so 

 fiercely, fighting with one another for it, and hasten- 

 ing back to ask for more. And so it has continued. 

 Their owner fears to feed them with it exclusively, 

 but gives them more or less daily, and the contrast 

 between their eagerness for the meat and their quiet 

 consumption of vegetables is a very instructive les- 

 son. Their stomachs, out on the plains, always 

 hold vegetable contents and nothing else. This was 

 doubtless the first piece of meat ever tasted by either 

 of these. Whence this craving appetite ? 



The experience of 1838 to which I referred was 

 this: That was in the earlier days of my 'natural 

 history,' three years before my first ichthyological 

 paper was written. I had taken three young Balti- 

 more orioles from their nest, but feared that I should 

 lose them, for they refused every variety of food I 

 offered them. At that time I was collecting birds 

 zealously, and was skinning several of them daily. 

 As I was preparing a specimen, one of the young ori- 

 oles was sitting on my table, very stupid indeed, 

 head drawn in, not life enough to utter a sound, 

 thoroughly dumpish. Without knowing why, I 

 picked up a bit of the bird's flesh and offered it to 

 him. To my great surprise he swallowed it on the 

 instant, and roused himself at once. That one 

 mouthful had done him so much good that he wanted 

 more. I took him on my finger and fed him piece 

 after piece, till his throat was swelled out like an 

 over fed chicken's crop, and I feared to give him 

 more. He settled himself down with great satisfac- 

 tion, and went to sleep. I fed his brother and sister 

 in the same way ; and from that time till they were 

 fully grown they had not a mouthful of food except 



the flesh of the birds I was skinning. Their eager- 

 ness for the meat was extreme. They learned the 

 bird-skinning business to perfection. As soon as they 

 saw me prepared for work, they all gathered about 

 the specimen, ravenous for meat, and I almost al- 

 ways commtenced to skin my bird, with an oriole sit- 

 ting on each hand, and one on the specimen itself, 

 and with three little heads down over the abdomen, 

 where the first cut was to be made (they knew the 

 point well enough): and the instant I opened the 

 skin, in went three bills, digging and tearing fiercely 

 for their food, and continuing at it as I continued 

 my work, till their appetites were satisfied. 



I do not know that this fact concerning the Balti- 

 more oriole has ever been reported. I recollect men- 

 tioning it to Mr. Audubon, but it was after his ac- 

 count of the species had been published. 



W. 0. Ayres. 

 New London, Conn., Aug. 11. 



Flooding the Sahara. 



In our own country an evaporation of two feet per 

 year is a small figure, and twice that amount lias 

 been recorded in some cases ; so that it would seem 

 to be safe to assume that it would exceed the latter 

 value in the north of Africa. Taking Mr. LeConte's 

 figures {Science, vol. viii. p. 35), and an evaporation 

 of two feet per year, and the cubic feet evaporated, 

 on an area of 3,100 square miles would be 2 X 864.- 

 230 X 10 5 cubic feet = 1,728,460 X 10 ^ cubic feet per 

 year. But the infiow, according to his assumptions, 

 would be 1,262,277X10^ cubic feet per year ; so that 

 at the rate of two feet of evaporation per year, the 

 amount evaporated would be 1.3 times the amount of 

 the inflow. In other words, at the rate of inflow 

 assumed, the depression to be flooded would never be 

 so far filled as to make a surface of 3,100 square 

 miles ; and if the evaporation be four feet per year, 

 the inflow would necessarily be nearly three times 

 that assumed by Mr. LeConte. 



De Volson Wood. 



Hoboken, Aug. 14. 



Barometer exposure. 



The discussions in Science relating to the effect of 

 high winds upon the indications of a barometer in a 

 room, have been highly interesting. I only desire at 

 this time to present a few facts that bear upon the 

 problem, and to correct a few misconceptions. No 

 one that has attempted making a fire in a very cold 

 room, on a very windy day, with a refractory chim- 

 ney in the fore ground, can be easily convinced that 

 there is much of a draft up a cold chimney, even with 

 a hurricane. Even if there were such draft, the air 

 must flow in through all the cracks, especially on the 

 windward side, and equilibrium would thus be kept 

 up. It should be noted also that the wind does not 

 blow steadily, but rather in gusts ; consequently there 

 can be no such thing as a permanent lower pressure 

 inside than outside a room, but a momentary depres- 

 sion by a gust would be relieved almost immediately 

 by the lull. 



This is shown beautifully by a barograph properly 

 arranged. All references will be to a barograph in- 

 closed in a tight glass case, such as has been adopted 

 by Mr. Hough of Albany. The fluctuations are so 

 rapid that they cannot be seen on a sheet carried at 

 the rate of one to two inches per day, but only upon 



