
+ 
Pate 
Vol. i No, 2,] Note on the calm region in the atmosphere, etc. 45 
V.8.J 
I have much pleasure in stating here that 1 am under a great 
obligation to Mr. James Watson, "Manager of the Gas Works. 
When, with ihe view of trying how far I vould rely on coal gas to 
give the elevation I desired, I asked Mr. Watson if he would ao 
me to inflate some of my balloons in his grounds, he not only h 
a suitable pipe fixed up, but he said that the gas required oy ine me 
for eT Wnee purposes would be at my disposal free of charge. 
believe these observations to be the first of the kind 
made in Calcutta, I will state in some detail what was done. The 
balloons used were of four sizes —2, 3, 44 and 6 feet in diameter 
respectively —made of what is called grease-proof tissue paper. 
As showing one of the practical difficulties I experienced, I ma 
calties to reach it which te would not trouble with for ordinary 
paper. My first consignment was ruined by these penetrating 
insects, 
The two eee sizes I used with hydrogen gas, the larger 
sizes with coal g I found that the six-foot balloons were about 
of the ‘material and the surface exposed to the un ide 
also found that the smaller balloons filled with hydrogen gave me 
almost as much information as the ] ger ones filled with coal gas, 
The greatest height the large balloons attiined was reckoned by me 
to be 10,000 feet, and I coud easily reach 4,000 with the two-foot 
balloon and 6,000 with the three-foot one. The heights given in 
this paper being all under 5,100, the Faery balloons were of suffi- 
cient rising power for my present purpos 
The measurements were made with a er of 3-inch ob- 
jective. At first I used a ruled glass diaphragm for measuring 
the size of the image of the balloon, but latterly I have used a 
micrometer. For all except pie gett small distances the 
focal length of te telescope may be taken to be 42 inches. i 
D be the diameter of the balloon in feet. / of the image inches 
the field aa view of the telescope, y the distance of the Ballet i in 
feet, we hav. 

y’ __ 42" 
Dp’ Be a’ 
or y=42 = coe feet for a balloon of 3’ diameter, # being 
wv 
the number of thousandths of an inch given by the micrometer. 
he micrometer was an ordinary reading micrometer with 
the larger divisions in hundredths of an inch. a could be easily 
subdivided to thousandths or even less. ‘There was. of course, a 
limit to accurate measurement due to the thickness of the threads 
of the micrometer and the difficulty of placing t the wires in an 
accurate a position to a small moving object. but I con- 
sider I made re iable measurements of the diameter of the image 
to five thbtenadths of an inch, 
