"Porter's telegraph college" on papers, "Densmore & Porter" on a book

http://chroniclingamerica.loc.gov/search/pages/results/?state=&date1=1836&date2=1922&proxtext=%E2%80%9DPorter%27s+telegraph+college%22&x=18&y=19&dateFilterType=yearRange&rows=20&searchType=basic

 http://hdl.handle.net/2027/nyp.33433006345817?urlappend=%3Bseq=53
The early history of the typewriter, by Chas. E. Weller...

Main Author:	Weller, Charles Edward, 1840-1925.
Language(s):	English
Published:	La Porte, Ind., Chase & Shepard, printers, 1918.
Subjects:	Sholes, Christopher Latham, > 1819-1890. Typewriters > History.
Physical Description:	87 p. incl. illus., port. 16 cm.

http://catalog.hathitrust.org/Record/001159266
Catalog Record: The early history of the typewriter | Hathi Trust Digital Library:

I suppose as follows:

• Porter's Telegraph college
• Porter's National Telegraph college 

There are some periods while Porter inform his typewriter to publication or not.

very short period  while 1868?

• Journal of the Telegraph, vol.1., No.16., July 1, 1868
• Perrysburg journal. (Perrysburg, Wood Co., O. [Ohio]), November 20, 1868, Image 4
•  Perrysburg journal. (Perrysburg, Wood Co., O. [Ohio]), November 27, 1868, Image 4
•  Perrysburg journal. (Perrysburg, Wood Co., O. [Ohio]), December 04, 1868, Image 4

or 1870?

What was said on the circular of his colleges?