7H 



THE POPULAR SCIENCE MONTHLY. 



As this dry cold air underruns the moist warm 

 air at the earth's surface, or as two areas of 

 high pressure flowing toward each other 

 must lift up the lighter air between them 

 and set it into cyclonic rotation, we must, 

 therefore, recognize the general conclusion 

 that Espy's aspiration cyclone as developed 

 by Fen-el is not the only form of cyclone, 

 but that those due to descending cold air, 

 and, therefore, having the general circula- 

 tion of the atmosphere as their fundamental 

 cause, are equally entitled to consideration. 

 To this last and latest development from the 

 theoretical side, I need only add that the 

 study of the motions of the clouds has en- 

 abled me to assert that there is no form of 

 motion known to the student of mechanics 

 of fluids but what is to be found beautifully 

 illustrated in some important phenomena of 

 the atmosphere. The experiments on the 

 motions of water and of air, and the meas- 

 urements thereon that you may make in a 

 well-appointed physical laboratory, are re- 

 peated by Nature on a large scale in the at- 

 mosphere." 



Antiquity of the Wheelbarrow. The in- 

 vention of the wheelbarrow has been gener- 

 ally ascribed to Blaise Pascal, who lived about 

 the middle of the sevententh century. M. 

 Littre, in his Dictionary, attributes it to one 

 Sieur Dupin, in 1669, seven years after Pas- 

 cal's death. M. Gaston Tissandier, however, 

 found in a copy of the Cosmography of Se- 

 bastian Munster, 1555, a curious woodcut 

 representing a wheelbarrow pushed by a 

 workman. Another plate in the same book 

 shows a tramway wagon running on rails. 

 Still earlier evidences of the existence of the 

 wheelbarrow have been found by if. Bixio 

 and M. F. Guerrero, who organized the retro- 

 spective exposition of the means of trans- 

 portation, which was held at Paris in 1889. 

 A manuscript history of the sangreal of the 

 thirteenth century contains' a picture of one 

 man shoving another in a wheelbarrow of a 

 style now in general use. A manuscript 

 Vita et Passio S. Dionysii Areopagi of the 

 fourteenth century, has a representation of a 

 wheelbarrow of another model, which is used 

 in carrying a bundle. A very artistic picture 

 in a manuscript La Vie et les Miracles de 

 Notre Dame of the fourteenth century, 

 represents a hospital where Sisters are tak- 



ing care of wounded, lame, deformed, or 

 paralytic persons, to which a man is wheel- 

 ing a new patient. A miniature in an illus- 

 trated edition of Quintus Curtius, of the 

 fourteenth century, shows a workman wheel- 

 ing building material, who is assisted in sus- 

 taining his load by a strap over his shoulders. 

 These evidences testify to the use of the 

 wheelbarrow as early as the thirteenth cent- 

 ury, and it may have been an old invention 

 then. 



Trees and Extreme Temperatures. The 



power of trees, says a note in Garden and 

 Forest, to regulate their own temperature to 

 a certain extent is seen in the fact that their 

 twigs are not frozen through in winter ; nor 

 does their temperature increase in summer 

 in proportion to the temperature of the sur- 

 rounding atmosphere. The bark is a bad 

 conductor of heat, and is to a certain extent 

 the clothing in which the plant is wrapped. 

 The surface evaporation of the leaves pro- 

 duces in summer a freshness in them that 

 causes them to feel cool even on hot days. 

 Evaporation, however, does not explain the 

 coolness of many kinds of fruit that are in- 

 closed in a hard envelope, through which it 

 seems almost impossible. Hooker mentions 

 a fruit grown by the Ganges in a soil hav- 

 ing a temperature of from 90 to 104, the 

 temperature of the juice of which had only 

 72 Fahr. 



Liquid Air and Liquid Oxygen. A lect- 

 ure was recently delivered at the Royal In- 

 stitution, London, by Prof. Dewar, embodying 

 the results of his recent investigations into 

 the properties of matter at excessively low 

 temperatures, and in particular of oxygen 

 and atmospheric air in the liquid condition. 

 The lecture was illustrated by experiments 

 such as have never before been attempted in 

 a lecture-room. Liquid oxygen was produced 

 in the presence of the audience literally by 

 pints, and liquid air was handed round in 

 claret glasses. While oxygen boils in air at 

 182 C. below zero, the researches of Lord 

 Kelvin and Prof. Tait indicate that tempera- 

 tures below 274 C. will not suspend all 

 the activities of matter. As this is far be- 

 low even the calculated boiling-point of liquid 

 hydrogen, the absolute zero seems to recede 

 as we advance. The purely chemical rela- 



