MR. JOHN COOK _has sent us a plan for taking cheaper pictures for stereoscopic purposes by means of a common camera, and the substitution for the ordinary ground glass of a piece of plate glass and a piece of paper, on which the outline of the figure is to be traced. When one sketch is thus made, the camera is to be moved fifteen or sixteen inches to the right or left, and a second drawing made in the same way. The plan is a very obvious one; and though adapted for those who can draw and have an ordinary camera, it presents few advantages to photographers._ H. H. H. (Ashburton). _Were we to recommend you to any particular maker for your collodion tent, we should deviate from our rule of impartiality where several vendors are concerned, and we would therefore refer you to our advertising columns._ W. N. (Kingston). _We are sorry we cannot afford space for answering all your Queries on the making of gun cotton. A portion made according to Dr. Diamond's formulary has been forwarded to your address; and if it is not_ entirely _soluble, then the fault is in your ether._ _A few complete sets of_ "NOTES AND QUERIES," Vols. i. _to_ vii., _price Three Guineas and a Half, may now be had; for which early application is desirable._ "NOTES AND QUERIES" _is published an noon on Friday, so that the Country Booksellers may receive Copies in that night's parcels, and deliver them to their Subscribers on the Saturday._ * * * * * {115} INDIGESTION, CONSTIPATION, NERVOUSNESS, &c.--BARRY, DU BARRY & CO.'S HEALTH-RESTORING FOOD for INVALIDS and INFANTS. THE REVALENTA ARABICA FOOD, the only natural, pleasant, and effectual remedy (without medicine, purging, inconvenience, or expense, as it saves fifty times its cost in other remedies) for nervous, stomachic, intestinal, liver and bilious complaints, however deeply rooted, dyspepsia (indigestion), habitual constipation, diarrhoea, acidity, heartburn, flatulency, oppression, distension, palpitation, eruption of the skin, rheumatism, gout, dropsy, sickness at the stomach during pregnancy, at sea, and under all other circumstances, debility in the aged as well as infants, fits, spasms, cramps, paralysis, &c. _A few out of 50,000 Cures:--_ Cure, No. 71, of dyspepsia; from the Right Hon. the Lord Stuart de Decies:--"I have derived considerable benefits from your Revalenta Arabica Food, and consider it due to yourselves and the public to authorise the publication of these lines.--STUART DE DECIES." Cure, No. 49,832:--"Fifty years' indescribable agony from dyspepsia, nervousness, asthma, cough, constipation, flatulency, spasms, sickness at the stomach, and vomitings have been removed by Du Barry's excellent food.--MARIA JOLLY, Wortham Ling, near Diss, Norfolk."