H. G. Brown & E. W. Clark
No. 11 Broadway
Whitehall, N. Y.
(Listed under H. G. Brown also)
The name E. W. Clark turns up often in searches but there is nothing to indicate which is the right one.
Many of the photographers of that era worked in other professions and did studio photography as a side-line. Hence, a census or city directory might identify them as "merchant" or "laborer" and the photography goes without credit.