NO. 2 METHOD OF REACHING EXTREME ALTITUDES 53 



But the actual resistance is R, multiplied by the relative density at 

 125,000 ft. which is approximately o.oi, giving for the resistance, 



F= 16,530 poundals/in.^ 



A retarding acceleration must therefore act upon the apparatus, of 



amount given by 



"p 



a= j^ = 16,530 ft./sec.^ 



Hence it is safe to say that, long before the apparatus had fallen to 

 the 125,000 ft. level, the velocity would have been reduced to, and 

 maintained at, a safe value, with the employment of even a small 

 parachute. This case, it should be noticed, is entirely different from 

 that of a falling meteor ; in that the apparatus under discussion falls 

 from rest, at the highest point reached, whereas the meteor enters 

 the earth's atmosphere with an enormous initial velocity. 



If it is considered desirable, for any reason, to dispense with a 

 sufficiently large parachute, the retarding of the apparatus may be 

 accomplished to any degree by having the rocket consist, at its highest 

 point of flight, not merely of instruments plus parachute, but of 

 instruments together with a chamber, and considerable propellant 

 material. Then, after the rocket has descended to some lower level, 

 let us say, to the upper limit of Sg, this propellant material can be 

 ejected, so that the velocity is considerably checked before the 

 apparatus reaches as low an altitude as, say, 5,000 ft. For the cases 

 in which the effective velocity, c(i— k), is as large as 7,000 ft. /sec. 

 there is little inconvenience in increasing the mass in this way. But 

 for the case in which c(i — k) =3,500, this method can hardly be as 

 satisfactory as the parachute method ; for if the " final " mass to be 

 elevated is made a number of pounds, let us say n, the " total initial 

 mass " (which is large even for one pound final mass) will be n fold 

 larger, and the apparatus correspondingly more expensive. 



APPLICATIONS TO DAILY OBSERVATIONS 

 Before leaving the subject of the attainment of high altitudes 

 within the earth's atmosphere, it will be well to mention briefly 

 another application of the method herein discussed: namely, to the 

 sending daily of small recording instruments to moderate altitudes, 

 such as five or six miles. As is already understood, simultaneous 

 daily observations of the vertical gradients of pressure, temperature, 

 and wind velocity, at a large number of stations would doubtless be 

 of great value in weather forecasting. The method herein described 



