34--When the invention or discovery is of a composition of matter the applicant shall furnish a specimen of the composition and of its ingredients sufficient in quantity for the purpose of experiment. 35--In all cases where the article is not perishable a specimen of the composition claimed, put up in proper form to be preserved in the office must be furnished. INTERFERENCES. 36--An interference is a proceeding instituted for the purpose of determining the question of priority of invention between two or more parties claiming substantially the same patentable invention or discovery. 37--If an application filed appears to claim substantially the same invention for which a _caveat_ has been filed, the Commissioner of Patents will notify the caveator to complete his application in three months, and if upon the filing thereof it appears to be in conflict an interference will be declared. If the caveator fails to complete his application within the time designated, or such further time as for cause shown may be granted to him, the Commissioner of Patents will proceed to examine the first named application as if there were no _caveat_. 38--Each party to the interference will be required to file a concise statement under oath showing the date of his original conception of the invention, of illustration by drawing or model, of its disclosure to others of its completion and of the extent of its use. 39--Testimony in such cases may be taken orally before the Commissioner of Patents, at such time as he may designate, or it may be taken by commission according to the forms usual in the Courts of the Republic. 40--After the testimony is closed the case shall be carefully examined by the Commissioner of Patents and adjudicated upon the proofs presented. CAVEATS. 41--A _caveat_ under the patent law is a notice given to the office of the caveator's claim as inventor, in order to prevent the grant of a patent to another for the same alleged invention upon an application filed during the life of the _caveat_, without notice to the caveator. 42--A _caveat_ may be filed in the Interior Department by any person who has made any new invention or discovery, and desires further time to mature the same, upon payment of the fee required by law. Such _caveat_ shall be preserved in secrecy, and shall be operative for the term of one year from the date of filing. 43--The _caveat_ must comprise a petition, a specification, an oath, and when the nature of the case admits of it, a drawing, and must be limited to a single invention or improvement. The attest of oath must comply with Rule 23. APPEALS.