Juke 21. 1883.] 



FOREST AND STREAM. 



413 



^i/ie and %rn$ fftootitlg, 



To inr-iire prompt attention, eommunieations should he ad- 

 d rested to ;/:■ ' Stream Pidjlishinii Co., and not to 



,■',■,,,',, ■■',■,' , ,,. in wlwst: alienee from the office malterx of i)tt- 

 portanre ore liable to delay. 



ATMOSPHERIC CONDITIONS AFFECTING INI- 

 TIAL VELOCITIES AND TRAJECTORIES 

 OF PROJECTILES. 



W 1 



a , ; a 



chiefly In 

 riilemai-. 

 tlie lmll.-i 



HV USIT, B. t. ZALtHSKfc U. S. A. 



isider the numerous conditions which ttu>cl accuracy 



weight, viz : Barometric pressure, temperature, and moisi 

 auiinaljnn of the follow tag table will indicate the relative in 

 of each of these. 



TABLE OF WEIGHTS OF AIR, PER CTJBIO FOOT, AT DIFFERENT 



TCRES. TUB BAROMETER BErSO AT A HEIOHT OF THIRTY INCHES AND 

 MOISTURE AT Gfi % PER CENT. OF SATURATION. 



Mean change of 

 weight for Mean change of Mean di 

 each tenth of] weight for ofweie 

 eh degree 

 tempera- 

 height of Ba- ture. (-100). 



-30° 



-•jll-d 



-10'- 1 



of scientific 1 

 match not to 

 cess. 

 Appended i 



I!, rv Hal 01 



ni ■■: ;■ 

 fen in c to rifi 

 tasted with a 

 r 



Th , ■ ta i 



, HiMl. I 



,,,, U |8 ::: 



'■: i ■ , ,p U | - 

 Thti Slin.jecl 



l. Effect of 



ectol 



3. EHeQtof 



1. EFFECT 



Powder rea 

 and thus vari 

 dorived-froni 



U 

 i .. ei i . i a lug 

 rwan 



was in-:. 



open v.' 

 must iir 



tin i! ma 

 tablo. - : 

 The 't- 

 1,310.8 



which tnav be 

 nee Note No. 

 itain Jolm E. 

 Hazard F. G. 



ed. Both kegs. 



•eported by the 



Tested here it 



"The 

 and a d 



■tails- are omitted. The mean initial velocity obtained was 

 ■ t ibles show an increase of 51.2 feetafter three days, drying 



y, when they 

 or a period of 

 the following 



Savnpk 



-, r pi 



S mpl 



No, I— Exposed three da 



; in heated room -1,389.8 feet, 

 n heated room— 1,395.0 feet, 

 in heated room=l, 106.6 feet. 

 se of velocity with time of expos- 

 I six days was much less than in 





,,, Hcai 



ingthe 

 the enl 



could b 

 ridges mat 

 all possibli 



il tbi 



amount of 

 befot '" 



wifhii 



the ci 



lute an ounl 



and M"' 

 lil I. ec 

 attire is higt 

 of the initial 

 air. 



To prpserv 



within the b 

 noteworl 03 

 breath .I .i.i 

 firings. 



Teniperati 

 perceptible 

 m heat in- ti 

 the relation 

 The first roll 

 velocities ot 

 (rerse effect 

 ing rounds a 

 | 



a. I .-_■] ■-;■ - 

 ' of lubri- 



i should be sufficient in number to cover 



practice and competition. Not alone 

 fiv dry. or at least containing a uniform 

 -iu s -Isold also be i ho; ottghly dried 



oca previous practice, as new and unknown 



-ture in i he air affects the initial velocity 



■•' . oto.i' ;is? iv.,iiiuiiiu deposited on the 



lis- hi"., -i'ls a ess ■"]' ies-. lvsss.1; se to til" 



ctile through the bore. The greater the abso- 



V pro-.. III , Ic.e "'"It" d""S I l"S 'Isi.'is:. ,.;.;. ;: 



projectile pass througli t'ne bore. As air is 

 -r absolute amount of moisture as the temper- 

 rations required are lessened let the increase, 

 as well as Hie reduction of resistance of the 



practioahle a uniform condition of moisture 



ain the deposit in a softener! condition, it is 

 members of the British team persistently 

 bore of their rifle in the intervals between 



jet initial velocities in that when it is Iowa 



lUhi toot, 01 meter ta o-abi 01 jpamnies respectively. Besides 

 height above the sea level, and latitude, three variables affect the 



.dity 



0.35 

 0.53 



o.™ 



1.03 

 1.-12 



a the above that an average change of 15.5- of tei 



t a 1 aigi . : "tire 1,'irj- i ' ta,;.-'- , 



barometer rarely exceed two-tenths (0.2) of ai 





iglu deer, 



ipera 



At Ft, Keogh. M 



ray within a 

 a below zero 



eight of air, 

 s with 



n Feb- 



in. the temperatur 

 S.2, to PJ1I- m August. ISS-;', a variation or itjrj-, giving a omer- 

 wight of air of lfilgrs. per cubic foot. 



tore reduces weiebt of air ov its elastic force, but the ex- 

 nutious produced bv this are' so inconsiderable, compared 

 anges produced by temperature, that ordinarily no great 

 11 result if the weight of the air is taken for a condition 



-is. ali 1 r ■.'.■!-.-'. I- ir.l- l'„l ' ;■ : "-" sea:, of smio ui a. II '• id 1 ,- 

 leiitn .I,,.,, .... , " eigV. : a.. ' i li" i --V.C" 1- hi 



3S of latitude affect the weight of the air in the ratio of the 

 : "g" (i.e., the accelerating force of gravity). This is so 

 it it need not be considered. The weights of air as given 



npiited for the latitude of New York City 



of ba 



•educed aboi 



e-tenth of ( 







Rasge ii 



,-Ya 





100 200 



300 400 



500 600 



700 



800 UoojlOOO'lloo 1200 



114011)1? 



list, in-i" 

 ilea 1031 

 112H 1021 

 1109 1011 



9ST 934 



•ISD <|er 



OIO 913 

 Oi'id SOS 

 910 879 



886 ! 844 

 878 Sid 

 Sad 87!) 

 ;47 Six 

 826 777 



732 



717 680 044 610 577 



691 051 614 578 545 



— — ■ 



_ 

















2.2 2.6 



3.1 3,4 



4.4 



4.8 



5.2 



S.5 5.9 6.3 6.6 (i.H 



0.26;0.30 



0.39,0.46 



0.51 



0.56 



0.G1 



0.135 0. 70 0.T3O.7; SO 



i--n ' |§& 



g Temperature. 





7 "i.-^ 



I ii^ti 



These two tables show marked results from changes of air density. 

 But they are thus far somewhat intangible to the practical rifleman 

 who does not concern himself much with l .remaining velocities" and 



■i line- ot e.i :. it. ' 11 .["--1 i a,,-, 1, ,;,.,! ..,, ire" ., - > eta. ::, o! .- a 



rounding conditions a'fectshis elevation— either in distance to be at- 



:.:iiiu 'I will, a est .an .a as ,, ,;. : .-.,■• ,, ,,s se-in-, a ."tia l . :;aa _-..■-; a r 



reqtured from the normal elevation of his sight 1 1 1 attain a given range 

 -or, in target, practice, the eipiivaleutchange in height on the target, 

 when using the normal ele cation scale. 



I have endeavored to give I be desired information in the following 

 table, which is the result of o, ai", atio sbaaed upon the data of the 

 two preceding tables, showing elevations with changes in range and 

 height on target due to variations of .emperature. and weight of air: 



+ Aqueous vapor has a specific gravity of 0.0235 when compared 

 with air taken as 1,1 000. This is apm-oxirnatelv %. When present 



in the. atmosphcie an'.?.-",: with air, it t-ecessarilv reduce^ the weighi 

 of a given volume of air. 



£■ S 9 9 s p 



ot approx 



An exat 

 very grea 



•lichee, 

 ample, 

 piratiir 



t may be i 

 nof thelai 



At this station 

 vation for l.OOOy 

 (in August, 1882) 



.-.yds. below the l.ooiivd. gi- 

 ft niiuimum of - 38° i Kcbn 

 iucreased to 



ige of t 

 10=80. 



OVC sea level) the ele- 

 ma\iiiiiiiii of 109°, 



Time. 



Barometer. 

 Inches. 



Temperature. 



Resulting weight 



of air.graiusper 



cubic foot. 



10 A. M. 



11 A. jI. 



12 M. 



1 P.M. 



2 P. 51. 



3 P. 31. 

 1 T. 31. 



80.00 

 30.00 



29.90 

 29.86 

 20 82 

 20.81 



72° 



Ml 



81° 

 86° 

 8S" 



72 

 70° 



519 

 509 

 507 



5(10 

 504 

 515 

 5IS 



We see that the minim 

 ninlmtim height of bar 

 educed the weight onb 



8 19 grains. If firing i 



ight oi air was not coincident with the 

 •. that the greatest fall of hnroim-ier 

 rains, while- the maximum diiTereuce 

 <■':-. -ri.-il. reduced the weight "f air 

 lesaa much as the reduction duoto 



