function g=g_cylinder(z,R,rho);
% Returns acceleration on surface of cylinder
% Usage: g=g_cylinder(z,R,rho)
%  where g is in mgal
%  z (height) and R (radius) in meters
%  rho (density) in gm/cc
%  note that you need to decide the sign of this acceleration.  If the
%  cyliner is above, subtract, if below add.
% JMB 4/90


g=2*pi*6.67e-11*rho*1000*(z+R-sqrt(z.^2+R^2))*1e5;
