MISCELLANY. 



253 



due to a non-homogeneous atmosphere pro- 

 duced by inequalities of temperature, and 

 the unequal distribution of vapor, " As I 

 stood upon the deck of the Irene," says 

 Prof. Tyndall, "pondering the question, I 

 became conscious of the exceeding power 

 of the sun beating against my back and 

 heating the objects near me. Beams of 

 equal power were falling on the sea, and 

 must have produced copious evaporation. 

 That the vapor generated should so rise 

 and mingle with the air as to form an abso- 

 lutely homogeneous mixture, I considered 

 in the highest degree improbable. It would 

 be sure, I thought, to streak and mottle the 

 atmosphere with spaces in which the air 

 would be in diflferent degrees saturated. . . . 

 At the limiting surfaces of these spaces, 

 though invisible, we should have the con- 

 ditions necessary to the production of par- 

 tial echoes and consequent waste of sound." 

 This philosophical explanation Prof. Tyn- 

 dall was able to verify. On one occasion, 

 when the air was opaque to sound, a cloud 

 arose and threw its shadow over the sea. 

 Some increase in the intensity of the sounds 

 was noticed ; but, with decline of the sun, 

 it was more obvious, until at length the 

 signal-sounds were heard at a distance of 

 twelve and three-quarter miles, when at first 

 they were inaudible at two miles. The in- 

 crease of distance at which the sounds were 

 distinctly heard was gradual with decline 

 of the sun, or, what is quite obvious, with 

 increase of homogeneity of the atmosphere. 

 This was fully shown on another occasion, 

 when, during a violent rain, the transmis- 

 sion of sounds was greatly increased, so 

 that they could be heard more distinctly at 

 seven and one-half miles than at five miles 

 previous to the storm. 



The Anderson School at Penikese,— The 



Anderson School of Natural History will 

 open this year on Tuesday, July 7th, and 

 close on Saturday, August 29th. During 

 the session. Prof. Mayer, of the Stevens In- 

 stitute, Hoboken, will deliver a course of 

 lectures on Physiological Physics. Mr, 

 Theodore Lyman, of the Cambridge Mu- 

 seum of Comparative Zoology, will give a 

 few lectures on Piscicvdture. Lectures will 

 also be delivered by Dr. W, S. Barnard, of 

 Ithaca, N, Y,, on Protozoa ; Prof. Jordan, of 



Appleton, Wis., will take charge of the in- 

 struction in Marine Botany. Mr. Alexander 

 Agassiz will have charge of the instruction 

 on Radiates and Embryology ; Dr. A. S. 

 Packard, Jr., of Salem, Mass., on Articu- 

 lates; Prof. B. G. Wilder, of Cornell, on 

 Vertebrates ; Prof. E. S. Morse, of Salem, 

 and Prof. C. E. Hamlin, of the Museum of 

 Comparative Zoology, on Mollusca; Mr. T. 

 W. Putnam, Director of the Peubody Acad- 

 emy of Science, on Fishes ; Mr. Edwin 

 Bicknell, of the Museum of Comparative 

 Zoology, on Microscopy. Instruction in 

 Drawing will be given by Mr. P. Roetter, of 

 the Museum of Comparative Zoology. Dr. 

 Packard and Mr, S. W, Garmon will take 

 charge of the dredging expedition, and the 

 laboratories will also be under the super- 

 vision of Mr. Garmon. 



Scientifie ipparatns. — While it cannot 

 be questioned that the popular demand in 

 this country for appUances with which to 

 illustrate the first principles of physical 

 science is well met by several makers of 

 philosophical instruments in this and other 

 cities, it is still true that, in the higher 

 branches and grades of scientific illustra- 

 tion, our chief dependence for efficient ap- 

 paratus is upon English, French, and Ger- 

 man makers. In the two great departments 

 of Electrics and Optics this is especially 

 observed, and we take pleasure in com- 

 mending to the notice of professors and 

 teachers of science the card of Mr, Brown- 

 ing, of London, in our advertising page this 

 month, Mr. Browning is an honored Fel- 

 low of the Royal Astronomical Society of 

 England, and, what is more to the present 

 purpose, he is the successful maker to the 

 Royal Society, and to the leading English 

 observatories, of the instruments they em- 

 ploy in their great and varied work. In 

 the construction of spectroscopes of every 

 sort he has, perhaps, no equal, certainly no 

 superior. 



Soaring and Sailing of Birds. — Mr. 



Belt, describing the movement of a pair 

 of black vultures sailing on the wind, 

 says : " Like all birds that soar, both over 

 sea and land, when it is calm the vultures 

 are obliged to flap their wings when they 

 fly; but when a breeze is blowing they are 



