In The Grand Canal of Ireland [David & Charles, Newton Abbot 1973], Ruth Delany says
In 1784 the construction of a link with the River Liffey had been discussed.
John Brownrigg had suggested a link from the Grand Canal Company’s harbour at James’s Street, but the plan eventually adopted was that of the Circular Line, the four-mile canal we have today, joining the Liffey via the Grand Canal Docks at Ringsend.
However, I have found a piece of evidence showing that the company considered the Liffey link ten years earlier, in 1774. Delany says that there are no board minutes for two years between 1773 and 1775, which would explain why this earlier plan has not hitherto been noticed. The evidence is from the Hibernian Journal; or, Chronicle of Liberty 19 October 1774.
The Trustees for executing the Canal of Communication between the Canal and the Harbour of Dublin, Toll free, confiding in the Favour of the Public for the Support of a Work of so great national Utility, have unanimously resolved upon the following Scheme, grafted upon the State Lottery for this present Year, for raising a Fund for that Purpose.
The Necessity of this Application to the Public at present, will appear from a Report of the Committee of Works of the Canal Company, certifying that the Works contracted for by Mr Traill between the Liffey at or near Sallins and the City Bason, are in such Forwardness as to render it absolutely necessary to proceed in making the above mentioned Communication early in the next Year; the said Report is in the Hands of the Secretary to the Canal Company.
2 prizes of £2000 is £4000
4 prizes of £750 is £3000
5 prizes of £150 is £750
10 prizes of £50 is £500
20 prizes of £40 is £400 *
40 prizes of £5 is £200
180 prizes of £1/10 is £270
600 prizes of £1 is £600
19150 prizes of £0/6 is £5740 *
First drawn first three days £40 is £120
Last drawn £200 is £200
£15780NB Not quite two Blanks to a Prize; and the Publick will take notice, that £35 is accounted for more than the Tickets will amount to.
Ten per Cent to be deducted from the Prizes for the Use of the Scheme.
15000 Tickets, 4 Numbers each, at £1 1s each to Subscribers for a Lot not less than 50 Tickets.
Price to Non-subscribers, one Guinea each Ticket.
Subscriptions are now receiving, and Tickets delivering out at the Navagation-house [sic] in Grafton-street, where the Prizes will be paid immediately after the Arrival of the Numerical Book from London. The Securities required from the Subscribers, viz Bankers Notes, Government and Fire-office Insurance Debentures, and City of Dublin Bonds, are to be lodged in the Bank of Thomas Finlay, Esq, and Company.
The Names of the Trustees for carrying the above Scheme into Execution, may be seen at the Navigation-House [sic], in Grafton-street.
There’s an idea for DAHG.
* sic
Irish waterways history 
If I’d known you were up in this neck of the woods, I’d have offered to hold the measuring tape!
Thank you. It was an unplanned stop, giving the dogs a breather en route to Dublin. bjg
Actually, this was an idea that was soon quashed since private companies were not legally permitted to benefit from public lottery schemes.
Excellent; thank you. Was the quashing related specifically to the canal scheme or were others trying it on? bjg
Yes, it was specific to their attempt. Legal opinion should have been sought before they published the ad. I’m hunting up the reference; it’s probably somewhere in the Calendar of Ancient Records.
Thank you very much for taking so much trouble: I am very grateful. bjg