Marketable Securities (Schedule of investment income) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2021	Jan. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Interest income	$ 67	$ 2,772	$ 294	$ 13,050
Dividend income	76,868	73,143	82,691	80,887
Gain on sale of marketable securities			83,176	46,981
Total	$ 76,935	$ 75,915	$ 166,161	$ 140,918