232 



Notes and Memoranda. 



conducting power imparted to it by increased moisture. Both these are agencies 

 of which the thermometer takes no notice. Its indications are furnished by the 

 contractions or expansions of a fluid, whether mercury or spirit, which always 

 maintains the same temperature as the surrounding medium, and accommodates 

 itself to these changes by altering its own density in the same proportion. The 

 living animal, on the contrary, as always maintaining a temperature of its own, 

 and as constantly resisting cooling agencies, is not to be considered as passively 

 submitting, like the fluid of the thermometer in its ordinary state. "When heated 

 to 90° Fahr., that being nearly the temperature of the surface of our bodies — in 

 the rapidity with which it is cooled, depending on the intensity of the cooling 

 influences, it furnishes an index to their combined effect. It does not depict the 

 force of any one of the cooling influences taken singly, but gives the sum of them 

 all acting simultaneously." The facts illustrated by the heated thermometer are 

 at least six in number, according to the experiments hitherto performed by Dr. 

 Osborne. It shows the conducting power of air and water ; the cooling effects of 

 currents of air and water ; the effect of wind in cooling the body and all other 

 objects of a higher temperature than itself ; the refrigerating effect of air admitted 

 into apartments ; the degree of heat derived from fires in rooms as compared 

 with the cooling effect of currents rushing towards the fire ; and the cold and heat 

 of climates as actually felt by human beings. It is evident that a heated thermo- 

 meter is capable of many useful applications. 



Re-introduction of Montgolfier Balloons. — The recent scientific ascents 

 that have been made by Mr. Glaisher and Mr. Coxwell, appear to have given a 

 new impulse to aerostation and to have removed it from the class of merely hazardous 

 amusements to the domain of science. In connection with these ascents we may 

 notice the re-introduction of Montgolfier or heated air balloons. It has long been 

 the opinion of many scientific men, that fire balloons are safer and much more 

 easily managed than such as are inflated either with pure hydrogen or the coal 

 gas which is now employed as a substitute. The prejudice against their employ- 

 ment has arisen from the supposed danger of the balloon taking fire from the 

 burning materials employed in rarefying the air, but this danger seems very much 

 overrated ; as far as we are aware, no accident from fire ever occurred to a simple 

 fire balloon. One fatal case occurred in Trance, in which two balloons were 

 employed, the upper filled with hydrogen, the lower with heated air, but the evil 

 result of this manifestly absurd arrangement does not militate against the employ- 

 ment of the simple Montgolfier balloon. M. Godard, an aeronaut attached to the 

 French army, has recently ascended from the Pre Catalan in a Montgolfier balloon 

 having a capacity of 4000 cubic metres, which can be inflated in less than half 

 'an hour ; the fuel used for the purpose being compressed cakes of rye straw. On 

 the last occasion he made a successful descent near Maisons, having performed the 

 journey in twenty six minutes. 



Horne and Thornthwaite's Equatorial Stand. — We have examined 

 the equatorial stand produced by the above-named opticians in answer to the 

 demand made by the possessors of moderate-sized telescopes — a demand which we 

 have reason to know has been much increased by the aid afforded to private 

 observers through the succession of astronomical papers in our own pages — and 

 we consider it an excellent instrument for the purpose, and at the price. It con- 

 sists of a firm pyramidal stand of cast-iron resting upon three bearing-screws, by 

 which, with the aid of the usual spirit-levels, the requisite adjustment can be 

 made. The declination and hour circles are six inches in diameter, and by means 

 of verniers can be read off with all the nicety that any ordinary observer can possi- 

 bly require. The polar axis is easily inclined to the angle needed by the latitude of 

 the place, and provision is made for fixing the telescope firmly, and securing it 

 precisely at right angles to the axis on which its vertical movements are made. The 

 motions are all smooth and steady, and the workmanship very good. 



